646644191 has 4 divisors (see below), whose sum is σ = 661682472. Its totient is φ = 631605912.

The previous prime is 646644143. The next prime is 646644203. The reversal of 646644191 is 191446646.

It is a happy number.

646644191 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 cyclic number.

It is not a de Polignac number, because 646644191 - 2²² = 642449887 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (646644101) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 7519076 + ... + 7519161.

It is an arithmetic number, because the mean of its divisors is an integer number (165420618).

Almost surely, 2^646644191 is an apocalyptic number.

646644191 is a deficient number, since it is larger than the sum of its proper divisors (15038281).

646644191 is a wasteful number, since it uses less digits than its factorization.

646644191 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 15038280.

The product of its digits is 124416, while the sum is 41.

The square root of 646644191 is about 25429.1995745049. The cubic root of 646644191 is about 864.7457976458.

The spelling of 646644191 in words is "six hundred forty-six million, six hundred forty-four thousand, one hundred ninety-one".