81635620 has 24 divisors (see below), whose sum is σ = 187020288. Its totient is φ = 29685600.

The previous prime is 81635599. The next prime is 81635623. The reversal of 81635620 is 2653618.

It is not an unprimeable number, because it can be changed into a prime (81635623) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 185316 + ... + 185755.

It is an arithmetic number, because the mean of its divisors is an integer number (7792512).

Almost surely, 2^81635620 is an apocalyptic number.

It is an amenable number.

81635620 is an abundant number, since it is smaller than the sum of its proper divisors (105384668).

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

81635620 is a wasteful number, since it uses less digits than its factorization.

81635620 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 371091 (or 371089 counting only the distinct ones).

The product of its (nonzero) digits is 8640, while the sum is 31.

The square root of 81635620 is about 9035.2432175343. The cubic root of 81635620 is about 433.8036799579.

The spelling of 81635620 in words is "eighty-one million, six hundred thirty-five thousand, six hundred twenty".