77946497721 has 45 divisors (see below), whose sum is σ = 118458271701. Its totient is φ = 51078185928.

The previous prime is 77946497711. The next prime is 77946497821. The reversal of 77946497721 is 12779464977.

The square root of 77946497721 is 279189.

It is a perfect power (a square), and thus also a powerful number.

77946497721 is a `hidden beast` number, since 7 + 79 + 4 + 6 + 497 + 72 + 1 = 666.

It is a de Polignac number, because none of the positive numbers 2^k-77946497721 is a prime.

It is not an unprimeable number, because it can be changed into a prime (77946497711) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 44 ways as a sum of consecutive naturals, for example, 168350736 + ... + 168351198.

Almost surely, 2^77946497721 is an apocalyptic number.

77946497721 is the 279189-th square number.

77946497721 is the 139595-th centered octagonal number.

It is an amenable number.

77946497721 is a deficient number, since it is larger than the sum of its proper divisors (40511773980).

77946497721 is an frugal number, since it uses more digits than its factorization.

77946497721 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1072 (or 533 counting only the distinct ones).

The product of its digits is 37340352, while the sum is 63.

The spelling of 77946497721 in words is "seventy-seven billion, nine hundred forty-six million, four hundred ninety-seven thousand, seven hundred twenty-one".