21706560 has 84 divisors (see below), whose sum is σ = 74671428. Its totient is φ = 5787648.

The previous prime is 21706537. The next prime is 21706561. The reversal of 21706560 is 6560712.

21706560 is a `hidden beast` number, since 2 + 1 + 7 + 0 + 656 + 0 = 666.

It can be written as a sum of positive squares in 2 ways, for example, as 8573184 + 13133376 = 2928^2 + 3624^2 .

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21706561) by changing a digit.

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 11 ways as a sum of consecutive naturals, for example, 889 + ... + 6648.

Almost surely, 2^21706560 is an apocalyptic number.

21706560 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 21706560, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (37335714).

21706560 is an abundant number, since it is smaller than the sum of its proper divisors (52964868).

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

21706560 is a wasteful number, since it uses less digits than its factorization.

21706560 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7560 (or 7547 counting only the distinct ones).

The product of its (nonzero) digits is 2520, while the sum is 27.

The square root of 21706560 is about 4659.0299419514. The cubic root of 21706560 is about 278.9525490659.

The spelling of 21706560 in words is "twenty-one million, seven hundred six thousand, five hundred sixty".