21257456 has 40 divisors (see below), whose sum is σ = 45198000. Its totient is φ = 9605120.

The previous prime is 21257419. The next prime is 21257461. The reversal of 21257456 is 65475212.

It is a congruent number.

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 7 ways as a sum of consecutive naturals, for example, 47120 + ... + 47568.

It is an arithmetic number, because the mean of its divisors is an integer number (1129950).

Almost surely, 2^21257456 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21257456, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (22599000).

21257456 is an abundant number, since it is smaller than the sum of its proper divisors (23940544).

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

21257456 is a wasteful number, since it uses less digits than its factorization.

21257456 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 737 (or 731 counting only the distinct ones).

The product of its digits is 16800, while the sum is 32.

The square root of 21257456 is about 4610.5808744669. The cubic root of 21257456 is about 277.0153041022.

The spelling of 21257456 in words is "twenty-one million, two hundred fifty-seven thousand, four hundred fifty-six".