665626391 has 2 divisors, whose sum is σ = 665626392. Its totient is φ = 665626390.

The previous prime is 665626363. The next prime is 665626397. The reversal of 665626391 is 193626566.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 665626391 - 2¹⁸ = 665364247 is a prime.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (665626397) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 332813195 + 332813196.

It is an arithmetic number, because the mean of its divisors is an integer number (332813196).

Almost surely, 2^665626391 is an apocalyptic number.

665626391 is a deficient number, since it is larger than the sum of its proper divisors (1).

665626391 is an equidigital number, since it uses as much as digits as its factorization.

665626391 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 349920, while the sum is 44.

The square root of 665626391 is about 25799.7362583419. The cubic root of 665626391 is about 873.1258459396.

The spelling of 665626391 in words is "six hundred sixty-five million, six hundred twenty-six thousand, three hundred ninety-one".