21781168 has 20 divisors (see below), whose sum is σ = 43231608. Its totient is φ = 10624640.

The previous prime is 21781157. The next prime is 21781171. The reversal of 21781168 is 86118712.

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 3 ways as a sum of consecutive naturals, for example, 15946 + ... + 17257.

Almost surely, 2^21781168 is an apocalyptic number.

It is an amenable number.

21781168 is a deficient number, since it is larger than the sum of its proper divisors (21450440).

21781168 is a wasteful number, since it uses less digits than its factorization.

21781168 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 33252 (or 33246 counting only the distinct ones).

The product of its digits is 5376, while the sum is 34.

The square root of 21781168 is about 4667.0298906264. The cubic root of 21781168 is about 279.2717811732.

The spelling of 21781168 in words is "twenty-one million, seven hundred eighty-one thousand, one hundred sixty-eight".