665656643 has 2 divisors, whose sum is σ = 665656644. Its totient is φ = 665656642.

The previous prime is 665656637. The next prime is 665656661. The reversal of 665656643 is 346656566.

It is a weak prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-665656643 is a prime.

It is not a weakly prime, because it can be changed into another prime (665656613) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 332828321 + 332828322.

It is an arithmetic number, because the mean of its divisors is an integer number (332828322).

Almost surely, 2^665656643 is an apocalyptic number.

665656643 is a deficient number, since it is larger than the sum of its proper divisors (1).

665656643 is an equidigital number, since it uses as much as digits as its factorization.

665656643 is an evil number, because the sum of its binary digits is even.

The product of its digits is 2332800, while the sum is 47.

The square root of 665656643 is about 25800.3225367436. The cubic root of 665656643 is about 873.1390732812.

The spelling of 665656643 in words is "six hundred sixty-five million, six hundred fifty-six thousand, six hundred forty-three".