21181868 has 12 divisors (see below), whose sum is σ = 37245432. Its totient is φ = 10540320.

The previous prime is 21181837. The next prime is 21181877. The reversal of 21181868 is 86818112.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 11705 + ... + 13392.

It is an arithmetic number, because the mean of its divisors is an integer number (3103786).

Almost surely, 2^21181868 is an apocalyptic number.

It is an amenable number.

21181868 is a deficient number, since it is larger than the sum of its proper divisors (16063564).

21181868 is a wasteful number, since it uses less digits than its factorization.

21181868 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 25312 (or 25310 counting only the distinct ones).

The product of its digits is 6144, while the sum is 35.

The square root of 21181868 is about 4602.3763427169. The cubic root of 21181868 is about 276.6865739454.

The spelling of 21181868 in words is "twenty-one million, one hundred eighty-one thousand, eight hundred sixty-eight".