665902639 has 4 divisors (see below), whose sum is σ = 665990424. Its totient is φ = 665814856.

The previous prime is 665902603. The next prime is 665902649. The reversal of 665902639 is 936209566.

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 665902639 - 2⁷ = 665902511 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 (665902649) 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, 31312 + ... + 48085.

It is an arithmetic number, because the mean of its divisors is an integer number (166497606).

Almost surely, 2^665902639 is an apocalyptic number.

665902639 is a deficient number, since it is larger than the sum of its proper divisors (87785).

665902639 is an equidigital number, since it uses as much as digits as its factorization.

665902639 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 87784.

The product of its (nonzero) digits is 524880, while the sum is 46.

The square root of 665902639 is about 25805.0894011240. The cubic root of 665902639 is about 873.2466173474.

The spelling of 665902639 in words is "six hundred sixty-five million, nine hundred two thousand, six hundred thirty-nine".