21785572 has 12 divisors (see below), whose sum is σ = 38174976. Its totient is φ = 10878440.

The previous prime is 21785549. The next prime is 21785579. The reversal of 21785572 is 27558712.

It is a super-2 number, since 2×21785572² = 949222294734368, which contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (21785579) by changing a digit.

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 3 ways as a sum of consecutive naturals, for example, 297 + ... + 6607.

It is an arithmetic number, because the mean of its divisors is an integer number (3181248).

Almost surely, 2^21785572 is an apocalyptic number.

It is an amenable number.

21785572 is a deficient number, since it is larger than the sum of its proper divisors (16389404).

21785572 is a wasteful number, since it uses less digits than its factorization.

21785572 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7178 (or 7176 counting only the distinct ones).

The product of its digits is 39200, while the sum is 37.

The square root of 21785572 is about 4667.5016871984. The cubic root of 21785572 is about 279.2906021725.

It can be divided in two parts, 2178 and 5572, that added together give a triangular number (7750 = T₁₂₄).

The spelling of 21785572 in words is "twenty-one million, seven hundred eighty-five thousand, five hundred seventy-two".