21759720 has 64 divisors (see below), whose sum is σ = 66813120. Its totient is φ = 5666304.

The previous prime is 21759713. The next prime is 21759721. The reversal of 21759720 is 2795712.

It is not an unprimeable number, because it can be changed into a prime (21759721) 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, 3052 + ... + 7268.

It is an arithmetic number, because the mean of its divisors is an integer number (1043955).

Almost surely, 2^21759720 is an apocalyptic number.

21759720 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 21759720, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (33406560).

21759720 is an abundant number, since it is smaller than the sum of its proper divisors (45053400).

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

21759720 is a wasteful number, since it uses less digits than its factorization.

21759720 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4274 (or 4270 counting only the distinct ones).

The product of its (nonzero) digits is 8820, while the sum is 33.

The square root of 21759720 is about 4664.7315035273. The cubic root of 21759720 is about 279.1800844025.

The spelling of 21759720 in words is "twenty-one million, seven hundred fifty-nine thousand, seven hundred twenty".