646665566646 has 48 divisors (see below), whose sum is σ = 1483403910912. Its totient is φ = 187439289840.

The previous prime is 646665566633. The next prime is 646665566681.

646665566646 is nontrivially palindromic in base 10.

It is a Harshad number since it is a multiple of its sum of digits (66).

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 19346866 + ... + 19380261.

It is an arithmetic number, because the mean of its divisors is an integer number (30904248144).

Almost surely, 2^646665566646 is an apocalyptic number.

646665566646 is a gapful number since it is divisible by the number (66) formed by its first and last digit.

646665566646 is an abundant number, since it is smaller than the sum of its proper divisors (836738344266).

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

646665566646 is a wasteful number, since it uses less digits than its factorization.

646665566646 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 38727177 (or 38727166 counting only the distinct ones).

The product of its digits is 671846400, while the sum is 66.

The spelling of 646665566646 in words is "six hundred forty-six billion, six hundred sixty-five million, five hundred sixty-six thousand, six hundred forty-six".