21256860 has 48 divisors (see below), whose sum is σ = 60977952. Its totient is φ = 5529600.

The previous prime is 21256847. The next prime is 21256867. The reversal of 21256860 is 6865212.

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

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21256867) by changing a digit.

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, 1861 + ... + 6780.

It is an arithmetic number, because the mean of its divisors is an integer number (1270374).

Almost surely, 2^21256860 is an apocalyptic number.

21256860 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21256860 is an abundant number, since it is smaller than the sum of its proper divisors (39721092).

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

21256860 is a wasteful number, since it uses less digits than its factorization.

21256860 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 8694 (or 8692 counting only the distinct ones).

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

The square root of 21256860 is about 4610.5162400755. The cubic root of 21256860 is about 277.0127151648.

The spelling of 21256860 in words is "twenty-one million, two hundred fifty-six thousand, eight hundred sixty".