665390623 has 4 divisors (see below), whose sum is σ = 676298728. Its totient is φ = 654482520.

The previous prime is 665390617. The next prime is 665390639. The reversal of 665390623 is 326093566.

It is a happy number.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 326093566 = 2 ⋅163046783.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-665390623 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 (665390653) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 5453961 + ... + 5454082.

It is an arithmetic number, because the mean of its divisors is an integer number (169074682).

Almost surely, 2^665390623 is an apocalyptic number.

665390623 is a deficient number, since it is larger than the sum of its proper divisors (10908105).

665390623 is a wasteful number, since it uses less digits than its factorization.

665390623 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 10908104.

The product of its (nonzero) digits is 174960, while the sum is 40.

The square root of 665390623 is about 25795.1666596671. The cubic root of 665390623 is about 873.0227453380.

The spelling of 665390623 in words is "six hundred sixty-five million, three hundred ninety thousand, six hundred twenty-three".