21587256 has 64 divisors (see below), whose sum is σ = 60480000. Its totient is φ = 7134048.

The previous prime is 21587233. The next prime is 21587257. The reversal of 21587256 is 65278512.

It is a happy number.

21587256 is a `hidden beast` number, since 21 + 587 + 2 + 56 = 666.

It is a Harshad number since it is a multiple of its sum of digits (36).

It is a self number, because there is not a number n which added to its sum of digits gives 21587256.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21587257) 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, 29665 + ... + 30383.

It is an arithmetic number, because the mean of its divisors is an integer number (945000).

Almost surely, 2^21587256 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 21587256, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (30240000).

21587256 is an abundant number, since it is smaller than the sum of its proper divisors (38892744).

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

21587256 is a wasteful number, since it uses less digits than its factorization.

21587256 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 873 (or 863 counting only the distinct ones).

The product of its digits is 33600, while the sum is 36.

The square root of 21587256 is about 4646.2087770568. The cubic root of 21587256 is about 278.4405484934.

The spelling of 21587256 in words is "twenty-one million, five hundred eighty-seven thousand, two hundred fifty-six".