77561394831 has 16 divisors (see below), whose sum is σ = 114935979520. Its totient is φ = 51694002360.

The previous prime is 77561394797. The next prime is 77561394877. The reversal of 77561394831 is 13849316577.

77561394831 is a `hidden beast` number, since 7 + 7 + 561 + 3 + 9 + 48 + 31 = 666.

It is not a de Polignac number, because 77561394831 - 2²¹ = 77559297679 is a prime.

It is a super-2 number, since 2×77561394831² (a number of 23 digits) contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (77561394431) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 272485 + ... + 478926.

It is an arithmetic number, because the mean of its divisors is an integer number (7183498720).

Almost surely, 2^77561394831 is an apocalyptic number.

77561394831 is a deficient number, since it is larger than the sum of its proper divisors (37374584689).

77561394831 is a wasteful number, since it uses less digits than its factorization.

77561394831 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 755243 (or 755237 counting only the distinct ones).

The product of its digits is 3810240, while the sum is 54.

The spelling of 77561394831 in words is "seventy-seven billion, five hundred sixty-one million, three hundred ninety-four thousand, eight hundred thirty-one".