665856557 has 2 divisors, whose sum is σ = 665856558. Its totient is φ = 665856556.

The previous prime is 665856511. The next prime is 665856571. The reversal of 665856557 is 755658566.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 656333161 + 9523396 = 25619^2 + 3086^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-665856557 is a prime.

It is a Chen prime.

It is a junction number, because it is equal to n+sod(n) for n = 665856499 and 665856508.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (665556557) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 332928278 + 332928279.

It is an arithmetic number, because the mean of its divisors is an integer number (332928279).

Almost surely, 2^665856557 is an apocalyptic number.

It is an amenable number.

665856557 is a deficient number, since it is larger than the sum of its proper divisors (1).

665856557 is an equidigital number, since it uses as much as digits as its factorization.

665856557 is an evil number, because the sum of its binary digits is even.

The product of its digits is 7560000, while the sum is 53.

The square root of 665856557 is about 25804.1964997944. The cubic root of 665856557 is about 873.2264733221.

The spelling of 665856557 in words is "six hundred sixty-five million, eight hundred fifty-six thousand, five hundred fifty-seven".