21588720 has 80 divisors (see below), whose sum is σ = 69852672. Its totient is φ = 5505280.

The previous prime is 21588713. The next prime is 21588727. The reversal of 21588720 is 2788512.

It is an interprime number because it is at equal distance from previous prime (21588713) and next prime (21588727).

It is a tau number, because it is divible by the number of its divisors (80).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21588727) 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, 3565 + ... + 7475.

Almost surely, 2^21588720 is an apocalyptic number.

21588720 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 21588720, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (34926336).

21588720 is an abundant number, since it is smaller than the sum of its proper divisors (48263952).

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

21588720 is a wasteful number, since it uses less digits than its factorization.

21588720 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3950 (or 3944 counting only the distinct ones).

The product of its (nonzero) digits is 8960, while the sum is 33.

The square root of 21588720 is about 4646.3663221920. The cubic root of 21588720 is about 278.4468427587.

It can be divided in two parts, 2158 and 8720, that added together give a triangular number (10878 = T₁₄₇).

The spelling of 21588720 in words is "twenty-one million, five hundred eighty-eight thousand, seven hundred twenty".