21109990 has 32 divisors (see below), whose sum is σ = 42425856. Its totient is φ = 7496160.

The previous prime is 21109987. The next prime is 21110027. The reversal of 21109990 is 9990112.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 2499 + ... + 6961.

It is an arithmetic number, because the mean of its divisors is an integer number (1325808).

Almost surely, 2^21109990 is an apocalyptic number.

21109990 is an abundant number, since it is smaller than the sum of its proper divisors (21315866).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21109990 is a wasteful number, since it uses less digits than its factorization.

21109990 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4524.

The product of its (nonzero) digits is 1458, while the sum is 31.

The square root of 21109990 is about 4594.5609148209. The cubic root of 21109990 is about 276.3732522637.

It can be divided in two parts, 2110 and 9990, that added together give a square (12100 = 110²).

The spelling of 21109990 in words is "twenty-one million, one hundred nine thousand, nine hundred ninety".