21640767923 has 2 divisors, whose sum is σ = 21640767924. Its totient is φ = 21640767922.

The previous prime is 21640767901. The next prime is 21640767931. The reversal of 21640767923 is 32976704612.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21640767923 - 2⁶ = 21640767859 is a prime.

It is not a weakly prime, because it can be changed into another prime (21640767983) 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 as a sum of consecutive naturals, namely, 10820383961 + 10820383962.

It is an arithmetic number, because the mean of its divisors is an integer number (10820383962).

Almost surely, 2^21640767923 is an apocalyptic number.

21640767923 is a deficient number, since it is larger than the sum of its proper divisors (1).

21640767923 is an equidigital number, since it uses as much as digits as its factorization.

21640767923 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 762048, while the sum is 47.

The spelling of 21640767923 in words is "twenty-one billion, six hundred forty million, seven hundred sixty-seven thousand, nine hundred twenty-three".