21813512 has 16 divisors (see below), whose sum is σ = 46743360. Its totient is φ = 9348624.

The previous prime is 21813511. The next prime is 21813527. The reversal of 21813512 is 21531812.

It is a happy number.

It is not an unprimeable number, because it can be changed into a prime (21813511) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 194708 + ... + 194819.

It is an arithmetic number, because the mean of its divisors is an integer number (2921460).

Almost surely, 2^21813512 is an apocalyptic number.

It is an amenable number.

21813512 is an abundant number, since it is smaller than the sum of its proper divisors (24929848).

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

21813512 is a wasteful number, since it uses less digits than its factorization.

21813512 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 389540 (or 389536 counting only the distinct ones).

The product of its digits is 480, while the sum is 23.

The square root of 21813512 is about 4670.4937640468. The cubic root of 21813512 is about 279.4099479158.

The spelling of 21813512 in words is "twenty-one million, eight hundred thirteen thousand, five hundred twelve".