21668923 has 2 divisors, whose sum is σ = 21668924. Its totient is φ = 21668922.

The previous prime is 21668917. The next prime is 21668929. The reversal of 21668923 is 32986612.

It is a balanced prime because it is at equal distance from previous prime (21668917) and next prime (21668929).

It is a cyclic number.

It is not a de Polignac number, because 21668923 - 2¹⁷ = 21537851 is a prime.

It is not a weakly prime, because it can be changed into another prime (21668929) by changing a digit.

It is a good prime.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10834461 + 10834462.

It is an arithmetic number, because the mean of its divisors is an integer number (10834462).

Almost surely, 2^21668923 is an apocalyptic number.

21668923 is a deficient number, since it is larger than the sum of its proper divisors (1).

21668923 is an equidigital number, since it uses as much as digits as its factorization.

21668923 is an evil number, because the sum of its binary digits is even.

The product of its digits is 31104, while the sum is 37.

The square root of 21668923 is about 4654.9890440258. The cubic root of 21668923 is about 278.7912305371.

The spelling of 21668923 in words is "twenty-one million, six hundred sixty-eight thousand, nine hundred twenty-three".