81564955 has 4 divisors (see below), whose sum is σ = 97877952. Its totient is φ = 65251960.

The previous prime is 81564943. The next prime is 81565007. The reversal of 81564955 is 55946518.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 55946518 = 2 ⋅27973259.

It is not a de Polignac number, because 81564955 - 2¹⁷ = 81433883 is a prime.

It is a Duffinian number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 8156491 + ... + 8156500.

It is an arithmetic number, because the mean of its divisors is an integer number (24469488).

Almost surely, 2^81564955 is an apocalyptic number.

81564955 is a deficient number, since it is larger than the sum of its proper divisors (16312997).

81564955 is a wasteful number, since it uses less digits than its factorization.

81564955 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 16312996.

The product of its digits is 216000, while the sum is 43.

The square root of 81564955 is about 9031.3318508402. The cubic root of 81564955 is about 433.6784748642.

The spelling of 81564955 in words is "eighty-one million, five hundred sixty-four thousand, nine hundred fifty-five".