81564417 has 48 divisors (see below), whose sum is σ = 135727488. Its totient is φ = 46717440.

The previous prime is 81564407. The next prime is 81564451. The reversal of 81564417 is 71446518.

It is a happy number.

81564417 is a `hidden beast` number, since 8 + 1 + 5 + 644 + 1 + 7 = 666.

It is not a de Polignac number, because 81564417 - 2⁴ = 81564401 is a prime.

It is not an unprimeable number, because it can be changed into a prime (81564407) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 257143 + ... + 257459.

It is an arithmetic number, because the mean of its divisors is an integer number (2827656).

Almost surely, 2^81564417 is an apocalyptic number.

It is an amenable number.

81564417 is a deficient number, since it is larger than the sum of its proper divisors (54163071).

81564417 is a wasteful number, since it uses less digits than its factorization.

81564417 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 470 (or 467 counting only the distinct ones).

The product of its digits is 26880, while the sum is 36.

The square root of 81564417 is about 9031.3020655939. The cubic root of 81564417 is about 433.6775213520.

The spelling of 81564417 in words is "eighty-one million, five hundred sixty-four thousand, four hundred seventeen".