21256824 has 32 divisors (see below), whose sum is σ = 54858240. Its totient is φ = 6856800.

The previous prime is 21256813. The next prime is 21256841. The reversal of 21256824 is 42865212.

It is a junction number, because it is equal to n+sod(n) for n = 21256791 and 21256800.

It is a congruent number.

It is an unprimeable number.

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 7 ways as a sum of consecutive naturals, for example, 13542 + ... + 15029.

It is an arithmetic number, because the mean of its divisors is an integer number (1714320).

Almost surely, 2^21256824 is an apocalyptic number.

21256824 is a gapful number since it is divisible by the number (24) formed by its first and last digit.

It is an amenable number.

21256824 is an abundant number, since it is smaller than the sum of its proper divisors (33601416).

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

21256824 is a wasteful number, since it uses less digits than its factorization.

21256824 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 28611 (or 28607 counting only the distinct ones).

The product of its digits is 7680, while the sum is 30.

The square root of 21256824 is about 4610.5123359557. The cubic root of 21256824 is about 277.0125587845.

The spelling of 21256824 in words is "twenty-one million, two hundred fifty-six thousand, eight hundred twenty-four".