21357923 has 2 divisors, whose sum is σ = 21357924. Its totient is φ = 21357922.

The previous prime is 21357913. The next prime is 21357929. The reversal of 21357923 is 32975312.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21357923 - 2⁶ = 21357859 is a prime.

It is a Sophie Germain prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21357923.

It is not a weakly prime, because it can be changed into another prime (21357929) 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 as a sum of consecutive naturals, namely, 10678961 + 10678962.

It is an arithmetic number, because the mean of its divisors is an integer number (10678962).

Almost surely, 2^21357923 is an apocalyptic number.

21357923 is a deficient number, since it is larger than the sum of its proper divisors (1).

21357923 is an equidigital number, since it uses as much as digits as its factorization.

21357923 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 11340, while the sum is 32.

The square root of 21357923 is about 4621.4632964030. The cubic root of 21357923 is about 277.4510283412.

The spelling of 21357923 in words is "twenty-one million, three hundred fifty-seven thousand, nine hundred twenty-three".