643647191 has 4 divisors (see below), whose sum is σ = 702160584. Its totient is φ = 585133800.

The previous prime is 643647161. The next prime is 643647197. The reversal of 643647191 is 191746346.

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 643647191 - 2⁶ = 643647127 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 (643647197) 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, 29256680 + ... + 29256701.

It is an arithmetic number, because the mean of its divisors is an integer number (175540146).

Almost surely, 2^643647191 is an apocalyptic number.

643647191 is a deficient number, since it is larger than the sum of its proper divisors (58513393).

643647191 is a wasteful number, since it uses less digits than its factorization.

643647191 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 58513392.

The product of its digits is 108864, while the sum is 41.

The square root of 643647191 is about 25370.2028174786. The cubic root of 643647191 is about 863.4077834489.

The spelling of 643647191 in words is "six hundred forty-three million, six hundred forty-seven thousand, one hundred ninety-one".