645651664663 has 4 divisors (see below), whose sum is σ = 645679210680. Its totient is φ = 645624118648.

The previous prime is 645651664597. The next prime is 645651664727. The reversal of 645651664663 is 366466156546.

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 645651664663 - 2²⁵ = 645618110231 is a prime.

It is a Smith number, since the sum of its digits (58) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 645651664598 and 645651664607.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (645651667663) 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, 13737820 + ... + 13784737.

It is an arithmetic number, because the mean of its divisors is an integer number (161419802670).

Almost surely, 2^645651664663 is an apocalyptic number.

645651664663 is a deficient number, since it is larger than the sum of its proper divisors (27546017).

645651664663 is a wasteful number, since it uses less digits than its factorization.

645651664663 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 27546016.

The product of its digits is 55987200, while the sum is 58.

The spelling of 645651664663 in words is "six hundred forty-five billion, six hundred fifty-one million, six hundred sixty-four thousand, six hundred sixty-three".