665913791 has 4 divisors (see below), whose sum is σ = 665980392. Its totient is φ = 665847192.

The previous prime is 665913769. The next prime is 665913823. The reversal of 665913791 is 197319566.

It is a happy number.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length.

It is a cyclic number.

It is not a de Polignac number, because 665913791 - 2⁶ = 665913727 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 (665913701) 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, 14921 + ... + 39426.

It is an arithmetic number, because the mean of its divisors is an integer number (166495098).

Almost surely, 2^665913791 is an apocalyptic number.

665913791 is a deficient number, since it is larger than the sum of its proper divisors (66601).

665913791 is a wasteful number, since it uses less digits than its factorization.

665913791 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 66600.

The product of its digits is 306180, while the sum is 47.

The square root of 665913791 is about 25805.3054816253. The cubic root of 665913791 is about 873.2514921301.

The spelling of 665913791 in words is "six hundred sixty-five million, nine hundred thirteen thousand, seven hundred ninety-one".