21506560 has 80 divisors (see below), whose sum is σ = 53425152. Its totient is φ = 8294400.

The previous prime is 21506533. The next prime is 21506593. The reversal of 21506560 is 6560512.

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

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 79225 + ... + 79495.

Almost surely, 2^21506560 is an apocalyptic number.

21506560 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 21506560, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (26712576).

21506560 is an abundant number, since it is smaller than the sum of its proper divisors (31918592).

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

21506560 is an equidigital number, since it uses as much as digits as its factorization.

21506560 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 325 (or 309 counting only the distinct ones).

The product of its (nonzero) digits is 1800, while the sum is 25.

The square root of 21506560 is about 4637.5165767898. The cubic root of 21506560 is about 278.0931661583.

The spelling of 21506560 in words is "twenty-one million, five hundred six thousand, five hundred sixty".