81177939961 has 32 divisors (see below), whose sum is σ = 86619456000. Its totient is φ = 75959520000.

The previous prime is 81177939959. The next prime is 81177939971. The reversal of 81177939961 is 16993977118.

It is a cyclic number.

It is not a de Polignac number, because 81177939961 - 2¹ = 81177939959 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (61).

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 81177939961.

It is not an unprimeable number, because it can be changed into a prime (81177939971) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 34527936 + ... + 34530286.

It is an arithmetic number, because the mean of its divisors is an integer number (2706858000).

Almost surely, 2^81177939961 is an apocalyptic number.

It is an amenable number.

81177939961 is a deficient number, since it is larger than the sum of its proper divisors (5441516039).

81177939961 is a wasteful number, since it uses less digits than its factorization.

81177939961 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2721.

The product of its digits is 5143824, while the sum is 61.

The spelling of 81177939961 in words is "eighty-one billion, one hundred seventy-seven million, nine hundred thirty-nine thousand, nine hundred sixty-one".