665437391 has 4 divisors (see below), whose sum is σ = 668198784. Its totient is φ = 662676000.

The previous prime is 665437343. The next prime is 665437397. The reversal of 665437391 is 193734566.

It is a happy number.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 665437391 - 2¹⁰ = 665436367 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (665437397) 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 in 3 ways as a sum of consecutive naturals, for example, 1380335 + ... + 1380816.

It is an arithmetic number, because the mean of its divisors is an integer number (167049696).

Almost surely, 2^665437391 is an apocalyptic number.

665437391 is a deficient number, since it is larger than the sum of its proper divisors (2761393).

665437391 is a wasteful number, since it uses less digits than its factorization.

665437391 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2761392.

The product of its digits is 408240, while the sum is 44.

The square root of 665437391 is about 25796.0731701552. The cubic root of 665437391 is about 873.0431987728.

The spelling of 665437391 in words is "six hundred sixty-five million, four hundred thirty-seven thousand, three hundred ninety-one".