21117866 has 32 divisors (see below), whose sum is σ = 39726720. Its totient is φ = 8179200.

The previous prime is 21117847. The next prime is 21117869. The reversal of 21117866 is 66871112.

It is a happy number.

It is not an unprimeable number, because it can be changed into a prime (21117869) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 36830 + ... + 37398.

It is an arithmetic number, because the mean of its divisors is an integer number (1241460).

Almost surely, 2^21117866 is an apocalyptic number.

21117866 is a deficient number, since it is larger than the sum of its proper divisors (18608854).

21117866 is a wasteful number, since it uses less digits than its factorization.

21117866 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 830.

The product of its digits is 4032, while the sum is 32.

The square root of 21117866 is about 4595.4179352916. The cubic root of 21117866 is about 276.4076190111.

Adding to 21117866 its reverse (66871112), we get a palindrome (87988978).

The spelling of 21117866 in words is "twenty-one million, one hundred seventeen thousand, eight hundred sixty-six".