21663686 has 16 divisors (see below), whose sum is σ = 37316160. Its totient is φ = 9328680.

The previous prime is 21663683. The next prime is 21663721. The reversal of 21663686 is 68636612.

It is a super-2 number, since 2×21663686² = 938630582213192, which contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (38).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21663683) 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 7 ways as a sum of consecutive naturals, for example, 25496 + ... + 26331.

It is an arithmetic number, because the mean of its divisors is an integer number (2332260).

Almost surely, 2^21663686 is an apocalyptic number.

21663686 is a deficient number, since it is larger than the sum of its proper divisors (15652474).

21663686 is a wasteful number, since it uses less digits than its factorization.

21663686 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 51859.

The product of its digits is 62208, while the sum is 38.

The square root of 21663686 is about 4654.4264952838. The cubic root of 21663686 is about 278.7687690714.

The spelling of 21663686 in words is "twenty-one million, six hundred sixty-three thousand, six hundred eighty-six".