81172388 has 12 divisors (see below), whose sum is σ = 154965552. Its totient is φ = 36896520.

The previous prime is 81172381. The next prime is 81172391. The reversal of 81172388 is 88327118.

It is a hoax number, since the sum of its digits (38) coincides with the sum of the digits of its distinct prime factors.

It is not an unprimeable number, because it can be changed into a prime (81172381) 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, 922370 + ... + 922457.

It is an arithmetic number, because the mean of its divisors is an integer number (12913796).

Almost surely, 2^81172388 is an apocalyptic number.

It is an amenable number.

81172388 is a deficient number, since it is larger than the sum of its proper divisors (73793164).

81172388 is a wasteful number, since it uses less digits than its factorization.

81172388 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1844842 (or 1844840 counting only the distinct ones).

The product of its digits is 21504, while the sum is 38.

The square root of 81172388 is about 9009.5720209120. The cubic root of 81172388 is about 432.9815999165.

The spelling of 81172388 in words is "eighty-one million, one hundred seventy-two thousand, three hundred eighty-eight".