21117566 has 8 divisors (see below), whose sum is σ = 31702440. Its totient is φ = 10550088.

The previous prime is 21117563. The next prime is 21117631. The reversal of 21117566 is 66571112.

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

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21117563) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 701 + ... + 6536.

It is an arithmetic number, because the mean of its divisors is an integer number (3962805).

Almost surely, 2^21117566 is an apocalyptic number.

21117566 is a deficient number, since it is larger than the sum of its proper divisors (10584874).

21117566 is a wasteful number, since it uses less digits than its factorization.

21117566 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 8698.

The product of its digits is 2520, while the sum is 29.

The square root of 21117566 is about 4595.3852939661. The cubic root of 21117566 is about 276.4063101245.

Adding to 21117566 its reverse (66571112), we get a palindrome (87688678).

The spelling of 21117566 in words is "twenty-one million, one hundred seventeen thousand, five hundred sixty-six".