21246539857 has 2 divisors, whose sum is σ = 21246539858. Its totient is φ = 21246539856.

The previous prime is 21246539827. The next prime is 21246539891. The reversal of 21246539857 is 75893564212.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 21245686081 + 853776 = 145759^2 + 924^2 .

It is a cyclic number.

It is not a de Polignac number, because 21246539857 - 2³¹ = 19099056209 is a prime.

It is not a weakly prime, because it can be changed into another prime (21246539827) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10623269928 + 10623269929.

It is an arithmetic number, because the mean of its divisors is an integer number (10623269929).

Almost surely, 2^21246539857 is an apocalyptic number.

It is an amenable number.

21246539857 is a deficient number, since it is larger than the sum of its proper divisors (1).

21246539857 is an equidigital number, since it uses as much as digits as its factorization.

21246539857 is an evil number, because the sum of its binary digits is even.

The product of its digits is 3628800, while the sum is 52.

The spelling of 21246539857 in words is "twenty-one billion, two hundred forty-six million, five hundred thirty-nine thousand, eight hundred fifty-seven".