21013256 has 32 divisors (see below), whose sum is σ = 43480800. Its totient is φ = 9440640.

The previous prime is 21013249. The next prime is 21013271. The reversal of 21013256 is 65231012.

It is an unprimeable number.

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 7 ways as a sum of consecutive naturals, for example, 6491 + ... + 9173.

It is an arithmetic number, because the mean of its divisors is an integer number (1358775).

Almost surely, 2^21013256 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 21013256, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (21740400).

21013256 is an abundant number, since it is smaller than the sum of its proper divisors (22467544).

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

21013256 is a wasteful number, since it uses less digits than its factorization.

21013256 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2789 (or 2785 counting only the distinct ones).

The product of its (nonzero) digits is 360, while the sum is 20.

The square root of 21013256 is about 4584.0218149568. The cubic root of 21013256 is about 275.9504566957.

Adding to 21013256 its reverse (65231012), we get a palindrome (86244268).

The spelling of 21013256 in words is "twenty-one million, thirteen thousand, two hundred fifty-six".