21088990 has 32 divisors (see below), whose sum is σ = 42206976. Its totient is φ = 7534080.

The previous prime is 21088979. The next prime is 21088997. The reversal of 21088990 is 9988012.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21088997) 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, 1414 + ... + 6646.

It is an arithmetic number, because the mean of its divisors is an integer number (1318968).

Almost surely, 2^21088990 is an apocalyptic number.

21088990 is an abundant number, since it is smaller than the sum of its proper divisors (21117986).

21088990 is a wasteful number, since it uses less digits than its factorization.

21088990 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5284.

The product of its (nonzero) digits is 10368, while the sum is 37.

The square root of 21088990 is about 4592.2750353175. The cubic root of 21088990 is about 276.2815774390.

The spelling of 21088990 in words is "twenty-one million, eighty-eight thousand, nine hundred ninety".