661856071245553 has 8 divisors (see below), whose sum is σ = 668687720226120. Its totient is φ = 655024593500160.

The previous prime is 661856071245521. The next prime is 661856071245581. The reversal of 661856071245553 is 355542170658166.

It can be written as a sum of positive squares in 4 ways, for example, as 384726570344704 + 277129500900849 = 19614448^2 + 16647207^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 661856071245553 - 2⁵ = 661856071245521 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (661856071245053) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 35031268 + ... + 50506453.

It is an arithmetic number, because the mean of its divisors is an integer number (83585965028265).

Almost surely, 2^{661856071245553} is an apocalyptic number.

It is an amenable number.

661856071245553 is a deficient number, since it is larger than the sum of its proper divisors (6831648980567).

661856071245553 is an equidigital number, since it uses as much as digits as its factorization.

661856071245553 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 85617587.

The product of its (nonzero) digits is 181440000, while the sum is 64.

The spelling of 661856071245553 in words is "six hundred sixty-one trillion, eight hundred fifty-six billion, seventy-one million, two hundred forty-five thousand, five hundred fifty-three".