21520490 has 16 divisors (see below), whose sum is σ = 39682440. Its totient is φ = 8398080.

The previous prime is 21520481. The next prime is 21520493. The reversal of 21520490 is 9402512.

It can be written as a sum of positive squares in 4 ways, for example, as 7689529 + 13830961 = 2773^2 + 3719^2 .

It is not an unprimeable number, because it can be changed into a prime (21520493) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 25835 + ... + 26654.

Almost surely, 2^21520490 is an apocalyptic number.

21520490 is a deficient number, since it is larger than the sum of its proper divisors (18161950).

21520490 is a wasteful number, since it uses less digits than its factorization.

21520490 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 52537.

The product of its (nonzero) digits is 720, while the sum is 23.

The square root of 21520490 is about 4639.0182150968. The cubic root of 21520490 is about 278.1531943812.

The spelling of 21520490 in words is "twenty-one million, five hundred twenty thousand, four hundred ninety".