21499920 has 120 divisors (see below), whose sum is σ = 77791896. Its totient is φ = 5289984.

The previous prime is 21499913. The next prime is 21499937. The reversal of 21499920 is 2999412.

It can be written as a sum of positive squares in 4 ways, for example, as 266256 + 21233664 = 516^2 + 4608^2 .

It is a tau number, because it is divible by the number of its divisors (120).

It is a Harshad number since it is a multiple of its sum of digits (36).

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (5) of ones.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 8212 + ... + 10508.

Almost surely, 2^21499920 is an apocalyptic number.

21499920 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21499920, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (38895948).

21499920 is an abundant number, since it is smaller than the sum of its proper divisors (56291976).

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

21499920 is a wasteful number, since it uses less digits than its factorization.

21499920 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2329 (or 2320 counting only the distinct ones).

The product of its (nonzero) digits is 11664, while the sum is 36.

The square root of 21499920 is about 4636.8006211180. The cubic root of 21499920 is about 278.0645434390.

The spelling of 21499920 in words is "twenty-one million, four hundred ninety-nine thousand, nine hundred twenty".