646191668721 has 32 divisors (see below), whose sum is σ = 868415109120. Its totient is φ = 427398523200.

The previous prime is 646191668719. The next prime is 646191668747. The reversal of 646191668721 is 127866191646.

646191668721 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is not a de Polignac number, because 646191668721 - 2¹ = 646191668719 is a prime.

It is not an unprimeable number, because it can be changed into a prime (646191668021) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 345371416 + ... + 345373286.

It is an arithmetic number, because the mean of its divisors is an integer number (27137972160).

Almost surely, 2^646191668721 is an apocalyptic number.

It is an amenable number.

646191668721 is a deficient number, since it is larger than the sum of its proper divisors (222223440399).

646191668721 is a wasteful number, since it uses less digits than its factorization.

646191668721 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3717.

The product of its digits is 5225472, while the sum is 57.

The spelling of 646191668721 in words is "six hundred forty-six billion, one hundred ninety-one million, six hundred sixty-eight thousand, seven hundred twenty-one".