21912240 has 80 divisors (see below), whose sum is σ = 77637888. Its totient is φ = 5008128.

The previous prime is 21912229. The next prime is 21912259. The reversal of 21912240 is 4221912.

It is a tau number, because it is divible by the number of its divisors (80).

It is a Harshad number since it is a multiple of its sum of digits (21).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 4842 + ... + 8201.

Almost surely, 2^21912240 is an apocalyptic number.

21912240 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21912240 is an abundant number, since it is smaller than the sum of its proper divisors (55725648).

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

21912240 is a wasteful number, since it uses less digits than its factorization.

21912240 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 13066 (or 13060 counting only the distinct ones).

The product of its (nonzero) digits is 288, while the sum is 21.

The square root of 21912240 is about 4681.0511640015. The cubic root of 21912240 is about 279.8308502171.

The spelling of 21912240 in words is "twenty-one million, nine hundred twelve thousand, two hundred forty".