21390570 has 24 divisors (see below), whose sum is σ = 55615716. Its totient is φ = 5704128.

The previous prime is 21390569. The next prime is 21390581. The reversal of 21390570 is 7509312.

21390570 is a `hidden beast` number, since 2 + 1 + 3 + 90 + 570 = 666.

It can be written as a sum of positive squares in 2 ways, for example, as 17715681 + 3674889 = 4209^2 + 1917^2 .

It is an unprimeable number.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 118747 + ... + 118926.

Almost surely, 2^21390570 is an apocalyptic number.

21390570 is an abundant number, since it is smaller than the sum of its proper divisors (34225146).

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

21390570 is a wasteful number, since it uses less digits than its factorization.

21390570 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 237686 (or 237683 counting only the distinct ones).

The product of its (nonzero) digits is 1890, while the sum is 27.

The square root of 21390570 is about 4624.9940540502. The cubic root of 21390570 is about 277.5923237973.

Adding to 21390570 its reverse (7509312), we get a palindrome (28899882).

The spelling of 21390570 in words is "twenty-one million, three hundred ninety thousand, five hundred seventy".