21402490 has 16 divisors (see below), whose sum is σ = 40790952. Its totient is φ = 8057344.

The previous prime is 21402481. The next prime is 21402499. The reversal of 21402490 is 9420412.

It is an interprime number because it is at equal distance from previous prime (21402481) and next prime (21402499).

It can be written as a sum of positive squares in 4 ways, for example, as 21169201 + 233289 = 4601^2 + 483^2 .

It is not an unprimeable number, because it can be changed into a prime (21402499) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 62779 + ... + 63118.

Almost surely, 2^21402490 is an apocalyptic number.

21402490 is a deficient number, since it is larger than the sum of its proper divisors (19388462).

21402490 is a wasteful number, since it uses less digits than its factorization.

21402490 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 125921.

The product of its (nonzero) digits is 576, while the sum is 22.

The square root of 21402490 is about 4626.2825248789. The cubic root of 21402490 is about 277.6438774501.

The spelling of 21402490 in words is "twenty-one million, four hundred two thousand, four hundred ninety".