665544391 has 2 divisors, whose sum is σ = 665544392. Its totient is φ = 665544390.

The previous prime is 665544361. The next prime is 665544437. The reversal of 665544391 is 193445566.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 665544391 - 2¹¹ = 665542343 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (665544361) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 332772195 + 332772196.

It is an arithmetic number, because the mean of its divisors is an integer number (332772196).

Almost surely, 2^665544391 is an apocalyptic number.

665544391 is a deficient number, since it is larger than the sum of its proper divisors (1).

665544391 is an equidigital number, since it uses as much as digits as its factorization.

665544391 is an evil number, because the sum of its binary digits is even.

The product of its digits is 388800, while the sum is 43.

The square root of 665544391 is about 25798.1470458636. The cubic root of 665544391 is about 873.0899903603.

The spelling of 665544391 in words is "six hundred sixty-five million, five hundred forty-four thousand, three hundred ninety-one".