665640751 has 2 divisors, whose sum is σ = 665640752. Its totient is φ = 665640750.

The previous prime is 665640719. The next prime is 665640757. The reversal of 665640751 is 157046566.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 665640751 - 2⁵ = 665640719 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (665640757) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 332820375 + 332820376.

It is an arithmetic number, because the mean of its divisors is an integer number (332820376).

Almost surely, 2^665640751 is an apocalyptic number.

665640751 is a deficient number, since it is larger than the sum of its proper divisors (1).

665640751 is an equidigital number, since it uses as much as digits as its factorization.

665640751 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 151200, while the sum is 40.

The square root of 665640751 is about 25800.0145542595. The cubic root of 665640751 is about 873.1321247356.

The spelling of 665640751 in words is "six hundred sixty-five million, six hundred forty thousand, seven hundred fifty-one".