21609560 has 64 divisors (see below), whose sum is σ = 56401920. Its totient is φ = 7297920.

The previous prime is 21609559. The next prime is 21609571. The reversal of 21609560 is 6590612.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 19337 + ... + 20423.

It is an arithmetic number, because the mean of its divisors is an integer number (881280).

Almost surely, 2^21609560 is an apocalyptic number.

21609560 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 21609560, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (28200960).

21609560 is an abundant number, since it is smaller than the sum of its proper divisors (34792360).

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

21609560 is a wasteful number, since it uses less digits than its factorization.

21609560 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1176 (or 1172 counting only the distinct ones).

The product of its (nonzero) digits is 3240, while the sum is 29.

The square root of 21609560 is about 4648.6083939175. The cubic root of 21609560 is about 278.5364106134.

The spelling of 21609560 in words is "twenty-one million, six hundred nine thousand, five hundred sixty".