646565691 has 4 divisors (see below), whose sum is σ = 862087592. Its totient is φ = 431043792.

The previous prime is 646565671. The next prime is 646565693. The reversal of 646565691 is 196565646.

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

It is not a de Polignac number, because 646565691 - 2¹⁸ = 646303547 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 646565691.

It is not an unprimeable number, because it can be changed into a prime (646565693) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 107760946 + ... + 107760951.

It is an arithmetic number, because the mean of its divisors is an integer number (215521898).

Almost surely, 2^646565691 is an apocalyptic number.

646565691 is a deficient number, since it is larger than the sum of its proper divisors (215521901).

646565691 is a wasteful number, since it uses less digits than its factorization.

646565691 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 215521900.

The product of its digits is 1166400, while the sum is 48.

The square root of 646565691 is about 25427.6560264606. The cubic root of 646565691 is about 864.7108040109.

The spelling of 646565691 in words is "six hundred forty-six million, five hundred sixty-five thousand, six hundred ninety-one".