646873985 has 4 divisors (see below), whose sum is σ = 776248788. Its totient is φ = 517499184.

The previous prime is 646873979. The next prime is 646874023. The reversal of 646873985 is 589378646.

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

It can be written as a sum of positive squares in 2 ways, for example, as 215854864 + 431019121 = 14692^2 + 20761^2 .

It is a cyclic number.

It is not a de Polignac number, because 646873985 - 2⁶ = 646873921 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 646873985.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 64687394 + ... + 64687403.

It is an arithmetic number, because the mean of its divisors is an integer number (194062197).

Almost surely, 2^646873985 is an apocalyptic number.

It is an amenable number.

646873985 is a deficient number, since it is larger than the sum of its proper divisors (129374803).

646873985 is a wasteful number, since it uses less digits than its factorization.

646873985 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 129374802.

The product of its digits is 8709120, while the sum is 56.

The square root of 646873985 is about 25433.7174829005. The cubic root of 646873985 is about 864.8482186602.

The spelling of 646873985 in words is "six hundred forty-six million, eight hundred seventy-three thousand, nine hundred eighty-five".