21256680 has 64 divisors (see below), whose sum is σ = 64088640. Its totient is φ = 5640192.

The previous prime is 21256679. The next prime is 21256691. The reversal of 21256680 is 8665212.

It is a Harshad number since it is a multiple of its sum of digits (30).

It is an unprimeable number.

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 15 ways as a sum of consecutive naturals, for example, 36552 + ... + 37128.

It is an arithmetic number, because the mean of its divisors is an integer number (1001385).

Almost surely, 2^21256680 is an apocalyptic number.

21256680 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 21256680, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (32044320).

21256680 is an abundant number, since it is smaller than the sum of its proper divisors (42831960).

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

21256680 is a wasteful number, since it uses less digits than its factorization.

21256680 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 898 (or 894 counting only the distinct ones).

The product of its (nonzero) digits is 5760, while the sum is 30.

The square root of 21256680 is about 4610.4967194436. The cubic root of 21256680 is about 277.0119332615.

The spelling of 21256680 in words is "twenty-one million, two hundred fifty-six thousand, six hundred eighty".