21784056 has 64 divisors (see below), whose sum is σ = 62791680. Its totient is φ = 6168960.

The previous prime is 21784043. The next prime is 21784067. The reversal of 21784056 is 65048712.

It is a super-2 number, since 2×21784056² = 949090191622272, which contains 22 as substring.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 20826 + ... + 21846.

It is an arithmetic number, because the mean of its divisors is an integer number (981120).

Almost surely, 2^21784056 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 21784056, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (31395840).

21784056 is an abundant number, since it is smaller than the sum of its proper divisors (41007624).

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

21784056 is a wasteful number, since it uses less digits than its factorization.

21784056 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1164 (or 1160 counting only the distinct ones).

The product of its (nonzero) digits is 13440, while the sum is 33.

The square root of 21784056 is about 4667.3392848603. The cubic root of 21784056 is about 279.2841236589.

The spelling of 21784056 in words is "twenty-one million, seven hundred eighty-four thousand, fifty-six".