21921240 has 64 divisors (see below), whose sum is σ = 71746560. Its totient is φ = 5313920.

The previous prime is 21921239. The next prime is 21921241. The reversal of 21921240 is 4212912.

It is an interprime number because it is at equal distance from previous prime (21921239) and next prime (21921241).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21921241) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 6984 + ... + 9623.

It is an arithmetic number, because the mean of its divisors is an integer number (1121040).

Almost surely, 2^21921240 is an apocalyptic number.

21921240 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21921240 is an abundant number, since it is smaller than the sum of its proper divisors (49825320).

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

21921240 is a wasteful number, since it uses less digits than its factorization.

21921240 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 16632 (or 16628 counting only the distinct ones).

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

The square root of 21921240 is about 4682.0123878520. The cubic root of 21921240 is about 279.8691565537.

The spelling of 21921240 in words is "twenty-one million, nine hundred twenty-one thousand, two hundred forty".