77729516591921 has 2 divisors, whose sum is σ = 77729516591922. Its totient is φ = 77729516591920.

The previous prime is 77729516591861. The next prime is 77729516591941. The reversal of 77729516591921 is 12919561592777.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 49530347328400 + 28199169263521 = 7037780^2 + 5310289^2 .

It is a cyclic number.

It is not a de Polignac number, because 77729516591921 - 2¹⁰ = 77729516590897 is a prime.

It is a super-2 number, since 2×77729516591921² (a number of 29 digits) contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (77729516591941) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 38864758295960 + 38864758295961.

It is an arithmetic number, because the mean of its divisors is an integer number (38864758295961).

Almost surely, 2^{77729516591921} is an apocalyptic number.

It is an amenable number.

77729516591921 is a deficient number, since it is larger than the sum of its proper divisors (1).

77729516591921 is an equidigital number, since it uses as much as digits as its factorization.

77729516591921 is an evil number, because the sum of its binary digits is even.

The product of its digits is 150028200, while the sum is 71.

The spelling of 77729516591921 in words is "seventy-seven trillion, seven hundred twenty-nine billion, five hundred sixteen million, five hundred ninety-one thousand, nine hundred twenty-one".