21613620 has 48 divisors (see below), whose sum is σ = 69164928. Its totient is φ = 4940160.

The previous prime is 21613619. The next prime is 21613639. The reversal of 21613620 is 2631612.

It is a happy number.

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 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, 25311 + ... + 26150.

It is an arithmetic number, because the mean of its divisors is an integer number (1440936).

Almost surely, 2^21613620 is an apocalyptic number.

21613620 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21613620 is an abundant number, since it is smaller than the sum of its proper divisors (47551308).

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

21613620 is a wasteful number, since it uses less digits than its factorization.

21613620 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 51480 (or 51478 counting only the distinct ones).

The product of its (nonzero) digits is 432, while the sum is 21.

The square root of 21613620 is about 4649.0450632361. The cubic root of 21613620 is about 278.5538533103.

The spelling of 21613620 in words is "twenty-one million, six hundred thirteen thousand, six hundred twenty".