81440538 has 32 divisors (see below), whose sum is σ = 167270400. Its totient is φ = 26420016.

The previous prime is 81440537. The next prime is 81440543. The reversal of 81440538 is 83504418.

It is a super-2 number, since 2×81440538² = 13265122459458888, which contains 22 as substring.

It is a junction number, because it is equal to n+sod(n) for n = 81440499 and 81440508.

It is not an unprimeable number, because it can be changed into a prime (81440531) 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, 123253 + ... + 123911.

It is an arithmetic number, because the mean of its divisors is an integer number (5227200).

Almost surely, 2^81440538 is an apocalyptic number.

81440538 is an abundant number, since it is smaller than the sum of its proper divisors (85829862).

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

81440538 is a wasteful number, since it uses less digits than its factorization.

81440538 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1186.

The product of its (nonzero) digits is 15360, while the sum is 33.

The square root of 81440538 is about 9024.4411461320. The cubic root of 81440538 is about 433.4578554698.

The spelling of 81440538 in words is "eighty-one million, four hundred forty thousand, five hundred thirty-eight".