81177993231 has 4 divisors (see below), whose sum is σ = 108237324312. Its totient is φ = 54118662152.

The previous prime is 81177993227. The next prime is 81177993283. The reversal of 81177993231 is 13239977118.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 81177993231 - 2² = 81177993227 is a prime.

It is a super-2 number, since 2×81177993231² (a number of 23 digits) contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81177994231) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 13529665536 + ... + 13529665541.

It is an arithmetic number, because the mean of its divisors is an integer number (27059331078).

Almost surely, 2^81177993231 is an apocalyptic number.

81177993231 is a deficient number, since it is larger than the sum of its proper divisors (27059331081).

81177993231 is a wasteful number, since it uses less digits than its factorization.

81177993231 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 27059331080.

The product of its digits is 571536, while the sum is 51.

The spelling of 81177993231 in words is "eighty-one billion, one hundred seventy-seven million, nine hundred ninety-three thousand, two hundred thirty-one".