Thematic Bible: Of the firstborn

As the redemption price for the 273 firstborn Israelites who outnumber the Levites, collect five shekels for each person, according to the standard sanctuary shekel-20 gerahs to the shekel. Give the money to Aaron and his sons as the redemption price for those who are in excess among the Israelites." read more.
So Moses collected the redemption money from those in excess of the ones redeemed by the Levites. He collected the money from the firstborn Israelites: 1,365 [shekels measured] by the standard sanctuary shekel. He gave the redemption money to Aaron and his sons in obedience to the Lord, just as the Lord commanded Moses.

The firstborn of every living thing, man or animal, presented to the Lord belongs to you. But you must certainly redeem the firstborn of man, and redeem the firstborn of an unclean animal. You will pay the redemption price for a month-old male according to your valuation: five shekels of silver by the standard sanctuary shekel, which is 20 gerahs.