81564938 has 16 divisors (see below), whose sum is σ = 150581760. Its totient is φ = 32267376.

The previous prime is 81564919. The next prime is 81564941. The reversal of 81564938 is 83946518.

It is a super-2 number, since 2×81564938² = 13305678221887688, which contains 22 as substring.

It is a Smith number, since the sum of its digits (44) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 223898 + ... + 224261.

It is an arithmetic number, because the mean of its divisors is an integer number (9411360).

Almost surely, 2^81564938 is an apocalyptic number.

81564938 is a deficient number, since it is larger than the sum of its proper divisors (69016822).

81564938 is a wasteful number, since it uses less digits than its factorization.

81564938 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 448181.

The product of its digits is 207360, while the sum is 44.

The square root of 81564938 is about 9031.3309096722. The cubic root of 81564938 is about 433.6784447347.

The spelling of 81564938 in words is "eighty-one million, five hundred sixty-four thousand, nine hundred thirty-eight".