21230520 has 32 divisors (see below), whose sum is σ = 63691920. Its totient is φ = 5661440.

The previous prime is 21230509. The next prime is 21230533. The reversal of 21230520 is 2503212.

It is a Harshad number since it is a multiple of its sum of digits (15).

It is a self number, because there is not a number n which added to its sum of digits gives 21230520.

It is a congruent number.

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, 88341 + ... + 88580.

Almost surely, 2^21230520 is an apocalyptic number.

21230520 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21230520 is an abundant number, since it is smaller than the sum of its proper divisors (42461400).

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

21230520 is a wasteful number, since it uses less digits than its factorization.

21230520 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 176935 (or 176931 counting only the distinct ones).

The product of its (nonzero) digits is 120, while the sum is 15.

The square root of 21230520 is about 4607.6588415376. The cubic root of 21230520 is about 276.8982496735.

Adding to 21230520 its reverse (2503212), we get a palindrome (23733732).

The spelling of 21230520 in words is "twenty-one million, two hundred thirty thousand, five hundred twenty".