21311866 has 8 divisors (see below), whose sum is σ = 32212224. Its totient is φ = 10574460.

The previous prime is 21311861. The next prime is 21311893. The reversal of 21311866 is 66811312.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not an unprimeable number, because it can be changed into a prime (21311861) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 40410 + ... + 40933.

It is an arithmetic number, because the mean of its divisors is an integer number (4026528).

Almost surely, 2^21311866 is an apocalyptic number.

21311866 is a deficient number, since it is larger than the sum of its proper divisors (10900358).

21311866 is a wasteful number, since it uses less digits than its factorization.

21311866 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 81476.

The product of its digits is 1728, while the sum is 28.

The square root of 21311866 is about 4616.4776615944. The cubic root of 21311866 is about 277.2514496584.

The spelling of 21311866 in words is "twenty-one million, three hundred eleven thousand, eight hundred sixty-six".