21890990 has 32 divisors (see below), whose sum is σ = 43352064. Its totient is φ = 7892640.

The previous prime is 21890987. The next prime is 21890993. The reversal of 21890990 is 9909812.

It is an interprime number because it is at equal distance from previous prime (21890987) and next prime (21890993).

It is a Smith number, since the sum of its digits (38) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21890993) 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 15 ways as a sum of consecutive naturals, for example, 13187 + ... + 14753.

It is an arithmetic number, because the mean of its divisors is an integer number (1354752).

Almost surely, 2^21890990 is an apocalyptic number.

21890990 is a deficient number, since it is larger than the sum of its proper divisors (21461074).

21890990 is a wasteful number, since it uses less digits than its factorization.

21890990 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1712.

The product of its (nonzero) digits is 11664, while the sum is 38.

The square root of 21890990 is about 4678.7808241036. The cubic root of 21890990 is about 279.7403630611.

The spelling of 21890990 in words is "twenty-one million, eight hundred ninety thousand, nine hundred ninety".