21012256 has 24 divisors (see below), whose sum is σ = 41537664. Its totient is φ = 10463040.

The previous prime is 21012241. The next prime is 21012259. The reversal of 21012256 is 65221012.

It is not an unprimeable number, because it can be changed into a prime (21012259) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 7461 + ... + 9883.

It is an arithmetic number, because the mean of its divisors is an integer number (1730736).

Almost surely, 2^21012256 is an apocalyptic number.

It is an amenable number.

21012256 is a deficient number, since it is larger than the sum of its proper divisors (20525408).

21012256 is a wasteful number, since it uses less digits than its factorization.

21012256 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2704 (or 2696 counting only the distinct ones).

The product of its (nonzero) digits is 240, while the sum is 19.

The square root of 21012256 is about 4583.9127391345. The cubic root of 21012256 is about 275.9460792235.

Adding to 21012256 its reverse (65221012), we get a palindrome (86233268).

The spelling of 21012256 in words is "twenty-one million, twelve thousand, two hundred fifty-six".