21668989 has 8 divisors (see below), whose sum is σ = 22320000. Its totient is φ = 21027552.

The previous prime is 21668963. The next prime is 21669007. The reversal of 21668989 is 98986612.

It is a happy number.

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

It is a cyclic number.

It is not a de Polignac number, because 21668989 - 2⁵ = 21668957 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21668929) 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, 2337 + ... + 6985.

It is an arithmetic number, because the mean of its divisors is an integer number (2790000).

Almost surely, 2^21668989 is an apocalyptic number.

It is an amenable number.

21668989 is a deficient number, since it is larger than the sum of its proper divisors (651011).

21668989 is an equidigital number, since it uses as much as digits as its factorization.

21668989 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4787.

The product of its digits is 373248, while the sum is 49.

The square root of 21668989 is about 4654.9961331885. The cubic root of 21668989 is about 278.7915135877.

The spelling of 21668989 in words is "twenty-one million, six hundred sixty-eight thousand, nine hundred eighty-nine".