21812990 has 16 divisors (see below), whose sum is σ = 39908160. Its totient is φ = 8581920.

The previous prime is 21812983. The next prime is 21813013. The reversal of 21812990 is 9921812.

21812990 = T₈₁₅ + T₈₁₆ + ... + T₈₇₅.

It is a happy number.

It is a congruent number.

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, 17270 + ... + 18489.

It is an arithmetic number, because the mean of its divisors is an integer number (2494260).

Almost surely, 2^21812990 is an apocalyptic number.

21812990 is a deficient number, since it is larger than the sum of its proper divisors (18095170).

21812990 is a wasteful number, since it uses less digits than its factorization.

21812990 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 35827.

The product of its (nonzero) digits is 2592, while the sum is 32.

The square root of 21812990 is about 4670.4378809700. The cubic root of 21812990 is about 279.4077191267.

The spelling of 21812990 in words is "twenty-one million, eight hundred twelve thousand, nine hundred ninety".