21256836 has 24 divisors (see below), whose sum is σ = 49725984. Its totient is φ = 7067520.

The previous prime is 21256813. The next prime is 21256841. The reversal of 21256836 is 63865212.

It is a junction number, because it is equal to n+sod(n) for n = 21256797 and 21256806.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 3151 + ... + 7241.

It is an arithmetic number, because the mean of its divisors is an integer number (2071916).

Almost surely, 2^21256836 is an apocalyptic number.

It is an amenable number.

21256836 is an abundant number, since it is smaller than the sum of its proper divisors (28469148).

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

21256836 is a wasteful number, since it uses less digits than its factorization.

21256836 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4531 (or 4529 counting only the distinct ones).

The product of its digits is 17280, while the sum is 33.

The square root of 21256836 is about 4610.5136373294. The cubic root of 21256836 is about 277.0126109113.

The spelling of 21256836 in words is "twenty-one million, two hundred fifty-six thousand, eight hundred thirty-six".