The account of the numbering begins with God's instructions to Moses and to Eleazar, Aaron's son:
Take the sum of all the congregation of the children of Israel, from
twenty years old and upward, throughout their fathers' house, all that
are able to go to war in Israel. (Numbers 26:2)
And the summary statement after the numbering is complete, is found here:
These were the numbered of the children of Israel, six hundred
thousand and a thousand seven hundred and thirty. (Numbers 26:51)
In both statements, the actual Hebrew word from which "children" was translated is "בְּנֵ֣י" (bə·nê). This literally means "sons," but is sometimes used to encompass a mixed group, so "children" is not necessarily a wrong translation. Just the same, a look at the Hebrew does not persuade us that women would have been included. If anything, it leans away from this.
There are texts within the same passage which translate this same word "בְּנֵ֣י" (bə·nê) as "sons," for example, verse 28 where we see the "sons of Joseph," verse 29 with "sons of Manasseh," etc.
The normal practice was to number the men--particularly those of age to be able to go to war. When women and children were included, a particular mention of this is made. In this passage, we do not see a special mention of women or of children except with those special cases where the daughters named had inherited their father's property because he had had no sons.
And Zelophehad the son of Hepher had no sons, but daughters: and the
names of the daughters of Zelophehad were Mahlah, and Noah, Hoglah,
Milcah, and Tirzah. (Numbers 26:33)
Subsequent explanations detail the reason, and precedent-setting policy which came of it, that these daughters were specifically named.
Then came the daughters of Zelophehad, the son of Hepher, the son of
Gilead, the son of Machir, the son of Manasseh, of the families of
Manasseh the son of Joseph: and these are the names of his daughters;
Mahlah, Noah, and Hoglah, and Milcah, and Tirzah. (Numbers 27:1)
The daughters of Zelophehad speak right: thou shalt surely give them a
possession of an inheritance among their father's brethren; and thou
shalt cause the inheritance of their father to pass unto them.
And they said, The LORD commanded my lord to give the land for an
inheritance by lot to the children of Israel: and my lord was
commanded by the LORD to give the inheritance of Zelophehad our
brother unto his daughters. (Numbers 36:2)
This is the thing which the LORD doth command concerning the daughters
of Zelophehad, saying, Let them marry to whom they think best; only to
the family of the tribe of their father shall they marry. (Numbers
Even as the LORD commanded Moses, so did the daughters of Zelophehad:
For Mahlah, Tirzah, and Hoglah, and Milcah, and Noah, the daughters of
Zelophehad, were married unto their father's brothers' sons: (Numbers
Plainly, these daughters were a special case in which they were appointed their father's inheritance in the absence of any brothers to whom it should ordinarily have been given.
Therefore, one might reasonably conclude that women and children were not generally included in this census, with the exception of these who had inherited their father's property.