21856724 has 6 divisors (see below), whose sum is σ = 38249274. Its totient is φ = 10928360.

The previous prime is 21856697. The next prime is 21856733. The reversal of 21856724 is 42765812.

It can be written as a sum of positive squares in only one way, i.e., 16483600 + 5373124 = 4060^2 + 2318^2 .

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 as a sum of consecutive naturals, namely, 2732087 + ... + 2732094.

It is an arithmetic number, because the mean of its divisors is an integer number (6374879).

Almost surely, 2^21856724 is an apocalyptic number.

It is an amenable number.

21856724 is a deficient number, since it is larger than the sum of its proper divisors (16392550).

21856724 is a wasteful number, since it uses less digits than its factorization.

21856724 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5464185 (or 5464183 counting only the distinct ones).

The product of its digits is 26880, while the sum is 35.

The square root of 21856724 is about 4675.1175386294. The cubic root of 21856724 is about 279.5943274992.

The spelling of 21856724 in words is "twenty-one million, eight hundred fifty-six thousand, seven hundred twenty-four".