636730721857 has 2 divisors, whose sum is σ = 636730721858. Its totient is φ = 636730721856.

The previous prime is 636730721839. The next prime is 636730721903. The reversal of 636730721857 is 758127037636.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 636574196736 + 156525121 = 797856^2 + 12511^2 .

It is a cyclic number.

It is not a de Polignac number, because 636730721857 - 2¹⁹ = 636730197569 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 636730721798 and 636730721807.

It is not a weakly prime, because it can be changed into another prime (636730721827) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 318365360928 + 318365360929.

It is an arithmetic number, because the mean of its divisors is an integer number (318365360929).

Almost surely, 2^636730721857 is an apocalyptic number.

It is an amenable number.

636730721857 is a deficient number, since it is larger than the sum of its proper divisors (1).

636730721857 is an equidigital number, since it uses as much as digits as its factorization.

636730721857 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 8890560, while the sum is 55.

The spelling of 636730721857 in words is "six hundred thirty-six billion, seven hundred thirty million, seven hundred twenty-one thousand, eight hundred fifty-seven".