21931530 has 32 divisors (see below), whose sum is σ = 55733184. Its totient is φ = 5504256.

The previous prime is 21931523. The next prime is 21931541. The reversal of 21931530 is 3513912.

It is a happy number.

It is a self number, because there is not a number n which added to its sum of digits gives 21931530.

It is an unprimeable number.

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 15 ways as a sum of consecutive naturals, for example, 20992 + ... + 22011.

It is an arithmetic number, because the mean of its divisors is an integer number (1741662).

Almost surely, 2^21931530 is an apocalyptic number.

21931530 is an abundant number, since it is smaller than the sum of its proper divisors (33801654).

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

21931530 is a wasteful number, since it uses less digits than its factorization.

21931530 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 43030.

The product of its (nonzero) digits is 810, while the sum is 24.

The square root of 21931530 is about 4683.1111453819. Note that the first 4 decimals coincide. The cubic root of 21931530 is about 279.9129406208.

The spelling of 21931530 in words is "twenty-one million, nine hundred thirty-one thousand, five hundred thirty".