21256320 has 64 divisors (see below), whose sum is σ = 67760640. Its totient is φ = 5667840.

The previous prime is 21256309. The next prime is 21256321. The reversal of 21256320 is 2365212.

It is a tau number, because it is divible by the number of its divisors (64).

It is a super-2 number, since 2×21256320² = 903662279884800, which contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (21256321) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 3616 + ... + 7455.

It is an arithmetic number, because the mean of its divisors is an integer number (1058760).

Almost surely, 2^21256320 is an apocalyptic number.

21256320 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21256320 is an abundant number, since it is smaller than the sum of its proper divisors (46504320).

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

21256320 is a wasteful number, since it uses less digits than its factorization.

21256320 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 11093 (or 11081 counting only the distinct ones).

The product of its (nonzero) digits is 720, while the sum is 21.

The square root of 21256320 is about 4610.4576779318. The cubic root of 21256320 is about 277.0103694416.

The spelling of 21256320 in words is "twenty-one million, two hundred fifty-six thousand, three hundred twenty".