21572420 has 24 divisors (see below), whose sum is σ = 45389400. Its totient is φ = 8612352.

The previous prime is 21572417. The next prime is 21572477. The reversal of 21572420 is 2427512.

It is a happy number.

It can be written as a sum of positive squares in 4 ways, for example, as 906304 + 20666116 = 952^2 + 4546^2 .

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, 19646 + ... + 20714.

It is an arithmetic number, because the mean of its divisors is an integer number (1891225).

Almost surely, 2^21572420 is an apocalyptic number.

21572420 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21572420 is an abundant number, since it is smaller than the sum of its proper divisors (23816980).

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

21572420 is a wasteful number, since it uses less digits than its factorization.

21572420 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2087 (or 2085 counting only the distinct ones).

The product of its (nonzero) digits is 1120, while the sum is 23.

The square root of 21572420 is about 4644.6119321209. The cubic root of 21572420 is about 278.3767471055.

Adding to 21572420 its reverse (2427512), we get a palindrome (23999932).

The spelling of 21572420 in words is "twenty-one million, five hundred seventy-two thousand, four hundred twenty".