645695917791 has 4 divisors (see below), whose sum is σ = 860927890392. Its totient is φ = 430463945192.

The previous prime is 645695917733. The next prime is 645695917819. The reversal of 645695917791 is 197719596546.

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 645695917791 - 2²⁹ = 645159046879 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (645695917091) 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, 107615986296 + ... + 107615986301.

It is an arithmetic number, because the mean of its divisors is an integer number (215231972598).

Almost surely, 2^645695917791 is an apocalyptic number.

645695917791 is a deficient number, since it is larger than the sum of its proper divisors (215231972601).

645695917791 is a wasteful number, since it uses less digits than its factorization.

645695917791 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 215231972600.

The product of its digits is 128595600, while the sum is 69.

The spelling of 645695917791 in words is "six hundred forty-five billion, six hundred ninety-five million, nine hundred seventeen thousand, seven hundred ninety-one".