21256704 has 120 divisors (see below), whose sum is σ = 70218720. Its totient is φ = 6064128.

The previous prime is 21256693. The next prime is 21256709. The reversal of 21256704 is 40765212.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21256709) 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 11 ways as a sum of consecutive naturals, for example, 31927 + ... + 32585.

It is an arithmetic number, because the mean of its divisors is an integer number (585156).

Almost surely, 2^21256704 is an apocalyptic number.

21256704 is a gapful number since it is divisible by the number (24) 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 21256704, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (35109360).

21256704 is an abundant number, since it is smaller than the sum of its proper divisors (48962016).

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

21256704 is an equidigital number, since it uses as much as digits as its factorization.

21256704 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 690 (or 671 counting only the distinct ones).

The product of its (nonzero) digits is 3360, while the sum is 27.

The square root of 21256704 is about 4610.4993221993. The cubic root of 21256704 is about 277.0120375155.

The spelling of 21256704 in words is "twenty-one million, two hundred fifty-six thousand, seven hundred four".