21921663 has 8 divisors (see below), whose sum is σ = 29665408. Its totient is φ = 14396184.

The previous prime is 21921659. The next prime is 21921667. The reversal of 21921663 is 36612912.

It is an interprime number because it is at equal distance from previous prime (21921659) and next prime (21921667).

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

It is not a de Polignac number, because 21921663 - 2² = 21921659 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21921663.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21921667) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 54331 + ... + 54732.

It is an arithmetic number, because the mean of its divisors is an integer number (3708176).

Almost surely, 2^21921663 is an apocalyptic number.

21921663 is a deficient number, since it is larger than the sum of its proper divisors (7743745).

21921663 is a wasteful number, since it uses less digits than its factorization.

21921663 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 109133.

The product of its digits is 3888, while the sum is 30.

The square root of 21921663 is about 4682.0575605176. The cubic root of 21921663 is about 279.8709566935.

The spelling of 21921663 in words is "twenty-one million, nine hundred twenty-one thousand, six hundred sixty-three".