21057490 has 16 divisors (see below), whose sum is σ = 38280600. Its totient is φ = 8339200.

The previous prime is 21057479. The next prime is 21057503. The reversal of 21057490 is 9475012.

It is a happy number.

It can be written as a sum of positive squares in 4 ways, for example, as 20912329 + 145161 = 4573^2 + 381^2 .

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, 9415 + ... + 11434.

Almost surely, 2^21057490 is an apocalyptic number.

21057490 is a deficient number, since it is larger than the sum of its proper divisors (17223110).

21057490 is a wasteful number, since it uses less digits than its factorization.

21057490 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 20957.

The product of its (nonzero) digits is 2520, while the sum is 28.

The square root of 21057490 is about 4588.8440810296. The cubic root of 21057490 is about 276.1439510226.

The spelling of 21057490 in words is "twenty-one million, fifty-seven thousand, four hundred ninety".