21382720 has 28 divisors (see below), whose sum is σ = 50918364. Its totient is φ = 8552960.

The previous prime is 21382717. The next prime is 21382723. The reversal of 21382720 is 2728312.

It is an interprime number because it is at equal distance from previous prime (21382717) and next prime (21382723).

It can be written as a sum of positive squares in 2 ways, for example, as 5125696 + 16257024 = 2264^2 + 4032^2 .

It is not an unprimeable number, because it can be changed into a prime (21382723) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 33091 + ... + 33730.

It is an arithmetic number, because the mean of its divisors is an integer number (1818513).

Almost surely, 2^21382720 is an apocalyptic number.

21382720 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21382720 is an abundant number, since it is smaller than the sum of its proper divisors (29535644).

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

21382720 is an equidigital number, since it uses as much as digits as its factorization.

21382720 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 66838 (or 66828 counting only the distinct ones).

The product of its (nonzero) digits is 1344, while the sum is 25.

The square root of 21382720 is about 4624.1453264360. The cubic root of 21382720 is about 277.5583623155.

Subtracting from 21382720 its product of nonzero digits (1344), we obtain a 4-th power (21381376 = 68⁴).

The spelling of 21382720 in words is "twenty-one million, three hundred eighty-two thousand, seven hundred twenty".