646663218 has 16 divisors (see below), whose sum is σ = 1301566080. Its totient is φ = 214181136.

The previous prime is 646663183. The next prime is 646663219. The reversal of 646663218 is 812366646.

It is a self number, because there is not a number n which added to its sum of digits gives 646663218.

It is not an unprimeable number, because it can be changed into a prime (646663219) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 342298 + ... + 344181.

It is an arithmetic number, because the mean of its divisors is an integer number (81347880).

Almost surely, 2^646663218 is an apocalyptic number.

646663218 is an abundant number, since it is smaller than the sum of its proper divisors (654902862).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

646663218 is a wasteful number, since it uses less digits than its factorization.

646663218 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 686641.

The product of its digits is 248832, while the sum is 42.

The square root of 646663218 is about 25429.5736889158. The cubic root of 646663218 is about 864.7542790524.

The spelling of 646663218 in words is "six hundred forty-six million, six hundred sixty-three thousand, two hundred eighteen".