21313920 has 128 divisors (see below), whose sum is σ = 72044640. Its totient is φ = 5341184.

The previous prime is 21313913. The next prime is 21313931. The reversal of 21313920 is 2931312.

It is a happy number.

It is a tau number, because it is divible by the number of its divisors (128).

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, 32314 + ... + 32966.

Almost surely, 2^21313920 is an apocalyptic number.

21313920 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 21313920, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (36022320).

21313920 is an abundant number, since it is smaller than the sum of its proper divisors (50730720).

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

21313920 is a wasteful number, since it uses less digits than its factorization.

21313920 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 692 (or 680 counting only the distinct ones).

The product of its (nonzero) digits is 324, while the sum is 21.

The square root of 21313920 is about 4616.7001202157. The cubic root of 21313920 is about 277.2603563739.

The spelling of 21313920 in words is "twenty-one million, three hundred thirteen thousand, nine hundred twenty".