668643646 has 32 divisors (see below), whose sum is σ = 1114702848. Its totient is φ = 298261440.

The previous prime is 668643641. The next prime is 668643653. The reversal of 668643646 is 646346866.

It is a self number, because there is not a number n which added to its sum of digits gives 668643646.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (668643641) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 357205 + ... + 359071.

It is an arithmetic number, because the mean of its divisors is an integer number (34834464).

Almost surely, 2^668643646 is an apocalyptic number.

668643646 is a deficient number, since it is larger than the sum of its proper divisors (446059202).

668643646 is a wasteful number, since it uses less digits than its factorization.

668643646 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2176.

The product of its digits is 2985984, while the sum is 49.

The square root of 668643646 is about 25858.1446743574. The cubic root of 668643646 is about 874.4431378164.

The spelling of 668643646 in words is "six hundred sixty-eight million, six hundred forty-three thousand, six hundred forty-six".