21613680 has 120 divisors (see below), whose sum is σ = 79213680. Its totient is φ = 5237760.

The previous prime is 21613673. The next prime is 21613693. The reversal of 21613680 is 8631612.

It is a tau number, because it is divible by the number of its divisors (120).

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 23 ways as a sum of consecutive naturals, for example, 6556 + ... + 9284.

It is an arithmetic number, because the mean of its divisors is an integer number (660114).

Almost surely, 2^21613680 is an apocalyptic number.

21613680 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 21613680, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (39606840).

21613680 is an abundant number, since it is smaller than the sum of its proper divisors (57600000).

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

21613680 is a wasteful number, since it uses less digits than its factorization.

21613680 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2759 (or 2750 counting only the distinct ones).

The product of its (nonzero) digits is 1728, while the sum is 27.

The square root of 21613680 is about 4649.0515161697. The cubic root of 21613680 is about 278.5541110677.

The spelling of 21613680 in words is "twenty-one million, six hundred thirteen thousand, six hundred eighty".