21138569723 has 2 divisors, whose sum is σ = 21138569724. Its totient is φ = 21138569722.

The previous prime is 21138569717. The next prime is 21138569779. The reversal of 21138569723 is 32796583112.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21138569723 - 2⁴ = 21138569707 is a prime.

It is a Sophie Germain prime.

It is not a weakly prime, because it can be changed into another prime (21138269723) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10569284861 + 10569284862.

It is an arithmetic number, because the mean of its divisors is an integer number (10569284862).

Almost surely, 2^21138569723 is an apocalyptic number.

21138569723 is a deficient number, since it is larger than the sum of its proper divisors (1).

21138569723 is an equidigital number, since it uses as much as digits as its factorization.

21138569723 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 544320, while the sum is 47.

The spelling of 21138569723 in words is "twenty-one billion, one hundred thirty-eight million, five hundred sixty-nine thousand, seven hundred twenty-three".