665641819 has 2 divisors, whose sum is σ = 665641820. Its totient is φ = 665641818.

The previous prime is 665641789. The next prime is 665641829. The reversal of 665641819 is 918146566.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 665641819 - 2¹¹ = 665639771 is a prime.

It is a super-2 number, since 2×665641819² = 886158062403257522, which contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (665641829) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 332820909 + 332820910.

It is an arithmetic number, because the mean of its divisors is an integer number (332820910).

Almost surely, 2^665641819 is an apocalyptic number.

665641819 is a deficient number, since it is larger than the sum of its proper divisors (1).

665641819 is an equidigital number, since it uses as much as digits as its factorization.

665641819 is an evil number, because the sum of its binary digits is even.

The product of its digits is 311040, while the sum is 46.

The square root of 665641819 is about 25800.0352519139. The cubic root of 665641819 is about 873.1325917066.

The spelling of 665641819 in words is "six hundred sixty-five million, six hundred forty-one thousand, eight hundred nineteen".