21613920 has 96 divisors (see below), whose sum is σ = 69981408. Its totient is φ = 5603328.

The previous prime is 21613909. The next prime is 21613931. The reversal of 21613920 is 2931612.

It is an interprime number because it is at equal distance from previous prime (21613909) and next prime (21613931).

It is a tau number, because it is divible by the number of its divisors (96).

It is a Harshad number since it is a multiple of its sum of digits (24).

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, 17152 + ... + 18368.

It is an arithmetic number, because the mean of its divisors is an integer number (728973).

Almost surely, 2^21613920 is an apocalyptic number.

21613920 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 21613920, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (34990704).

21613920 is an abundant number, since it is smaller than the sum of its proper divisors (48367488).

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

21613920 is a wasteful number, since it uses less digits than its factorization.

21613920 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1272 (or 1264 counting only the distinct ones).

The product of its (nonzero) digits is 648, while the sum is 24.

The square root of 21613920 is about 4649.0773278146. The cubic root of 21613920 is about 278.5551420928. Note that the first 3 decimals are identical.

The spelling of 21613920 in words is "twenty-one million, six hundred thirteen thousand, nine hundred twenty".