646666646 has 4 divisors (see below), whose sum is σ = 969999972. Its totient is φ = 323333322.

The previous prime is 646666639. The next prime is 646666661.

646666646 is nontrivially palindromic in base 10.

646666646 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

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

It is a junction number, because it is equal to n+sod(n) for n = 646666594 and 646666603.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 161666660 + ... + 161666663.

It is an arithmetic number, because the mean of its divisors is an integer number (242499993).

Almost surely, 2^646666646 is an apocalyptic number.

646666646 is a deficient number, since it is larger than the sum of its proper divisors (323333326).

646666646 is a wasteful number, since it uses less digits than its factorization.

646666646 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 323333325.

The product of its digits is 4478976, while the sum is 50.

The square root of 646666646 is about 25429.6410906643. The cubic root of 646666646 is about 864.7558070876.

The spelling of 646666646 in words is "six hundred forty-six million, six hundred sixty-six thousand, six hundred forty-six".