77 is: the 22nd discrete semiprime and the first of the (7.q) family, where q is a higher prime. with a prime aliquot sum of 19 within an aliquot sequence (77, 19, 1, 0) to the Prime in the 19-aliquot tree. 77 is the second composite member of the 19-aliquot tree with 65 a Blum integer since both 7 and 11 are Gaussian primes. the sum of three consecutive squares, 42 + 52 + 62. the sum of the first eight prime numbers. the number of integer partitions of the number 12. the largest number that cannot be written as a sum of distinct numbers whose reciprocals sum to 1. the number of digits of the 12th perfect number. It is possible for a sudoku puzzle to have as many as 77 givens, yet lack a unique solution. It and 49 are the only 2-digit numbers whose home primes (in base 10) have not been calculated.
