21856436 has 12 divisors (see below), whose sum is σ = 43712928. Its totient is φ = 9367032.

The previous prime is 21856423. The next prime is 21856451. The reversal of 21856436 is 63465812.

21856436 is an admirable number.

It is a junction number, because it is equal to n+sod(n) for n = 21856396 and 21856405.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 390266 + ... + 390321.

It is an arithmetic number, because the mean of its divisors is an integer number (3642744).

Almost surely, 2^21856436 is an apocalyptic number.

It is an amenable number.

21856436 is a primitive abundant number, since it is smaller than the sum of its proper divisors, none of which is abundant.

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

21856436 is a wasteful number, since it uses less digits than its factorization.

21856436 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 780598 (or 780596 counting only the distinct ones).

The product of its digits is 34560, while the sum is 35.

The square root of 21856436 is about 4675.0867371633. The cubic root of 21856436 is about 279.5930994481.

The spelling of 21856436 in words is "twenty-one million, eight hundred fifty-six thousand, four hundred thirty-six".