81391368 has 32 divisors (see below), whose sum is σ = 210044160. Its totient is φ = 26255040.

The previous prime is 81391363. The next prime is 81391397. The reversal of 81391368 is 86319318.

It is a super-2 number, since 2×81391368² = 13249109569822848, which contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (81391361) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 53955 + ... + 55442.

It is an arithmetic number, because the mean of its divisors is an integer number (6563880).

Almost surely, 2^81391368 is an apocalyptic number.

It is an amenable number.

81391368 is an abundant number, since it is smaller than the sum of its proper divisors (128652792).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

81391368 is a wasteful number, since it uses less digits than its factorization.

81391368 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 109437 (or 109433 counting only the distinct ones).

The product of its digits is 31104, while the sum is 39.

The square root of 81391368 is about 9021.7164663937. The cubic root of 81391368 is about 433.3706040264.

The spelling of 81391368 in words is "eighty-one million, three hundred ninety-one thousand, three hundred sixty-eight".