21921868 has 24 divisors (see below), whose sum is σ = 39170880. Its totient is φ = 10732800.

The previous prime is 21921847. The next prime is 21921869. The reversal of 21921868 is 86812912.

It is not an unprimeable number, because it can be changed into a prime (21921869) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 54468 + ... + 54868.

It is an arithmetic number, because the mean of its divisors is an integer number (1632120).

Almost surely, 2^21921868 is an apocalyptic number.

It is an amenable number.

21921868 is a deficient number, since it is larger than the sum of its proper divisors (17249012).

21921868 is a wasteful number, since it uses less digits than its factorization.

21921868 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 657 (or 655 counting only the distinct ones).

The product of its digits is 13824, while the sum is 37.

The square root of 21921868 is about 4682.0794525510. The cubic root of 21921868 is about 279.8718290934.

The spelling of 21921868 in words is "twenty-one million, nine hundred twenty-one thousand, eight hundred sixty-eight".