21312560 has 40 divisors (see below), whose sum is σ = 52469856. Its totient is φ = 8023040.

The previous prime is 21312539. The next prime is 21312587. The reversal of 21312560 is 6521312.

It is a tau number, because it is divible by the number of its divisors (40).

It is a Harshad number since it is a multiple of its sum of digits (20).

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, 6476 + ... + 9195.

Almost surely, 2^21312560 is an apocalyptic number.

21312560 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21312560 is an abundant number, since it is smaller than the sum of its proper divisors (31157296).

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

21312560 is a wasteful number, since it uses less digits than its factorization.

21312560 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 15701 (or 15695 counting only the distinct ones).

The product of its (nonzero) digits is 360, while the sum is 20.

The square root of 21312560 is about 4616.5528265146. The cubic root of 21312560 is about 277.2544590995.

Adding to 21312560 its reverse (6521312), we get a palindrome (27833872).

The spelling of 21312560 in words is "twenty-one million, three hundred twelve thousand, five hundred sixty".