81656420 has 24 divisors (see below), whose sum is σ = 175662648. Its totient is φ = 31865600.

The previous prime is 81656401. The next prime is 81656453. The reversal of 81656420 is 2465618.

It can be written as a sum of positive squares in 4 ways, for example, as 4778596 + 76877824 = 2186^2 + 8768^2 .

It is a super-3 number, since 3×81656420³ (a number of 25 digits) contains 333 as substring.

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, 48971 + ... + 50610.

It is an arithmetic number, because the mean of its divisors is an integer number (7319277).

Almost surely, 2^81656420 is an apocalyptic number.

It is an amenable number.

81656420 is an abundant number, since it is smaller than the sum of its proper divisors (94006228).

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

81656420 is a wasteful number, since it uses less digits than its factorization.

81656420 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 99631 (or 99629 counting only the distinct ones).

The product of its (nonzero) digits is 11520, while the sum is 32.

The square root of 81656420 is about 9036.3941923756. The cubic root of 81656420 is about 433.8405198828.

The spelling of 81656420 in words is "eighty-one million, six hundred fifty-six thousand, four hundred twenty".