661856013953 has 2 divisors, whose sum is σ = 661856013954. Its totient is φ = 661856013952.

The previous prime is 661856013899. The next prime is 661856013961. The reversal of 661856013953 is 359310658166.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 632489365264 + 29366648689 = 795292^2 + 171367^2 .

It is a cyclic number.

It is not a de Polignac number, because 661856013953 - 2²² = 661851819649 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 661856013895 and 661856013904.

It is not a weakly prime, because it can be changed into another prime (661856018953) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 330928006976 + 330928006977.

It is an arithmetic number, because the mean of its divisors is an integer number (330928006977).

Almost surely, 2^661856013953 is an apocalyptic number.

It is an amenable number.

661856013953 is a deficient number, since it is larger than the sum of its proper divisors (1).

661856013953 is an equidigital number, since it uses as much as digits as its factorization.

661856013953 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 3499200, while the sum is 53.

The spelling of 661856013953 in words is "six hundred sixty-one billion, eight hundred fifty-six million, thirteen thousand, nine hundred fifty-three".