645736945877 has 4 divisors (see below), whose sum is σ = 645826926156. Its totient is φ = 645646965600.

The previous prime is 645736945871. The next prime is 645736945913. The reversal of 645736945877 is 778549637546.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 778549637546 = 2 ⋅389274818773.

It can be written as a sum of positive squares in 2 ways, for example, as 484936747876 + 160800198001 = 696374^2 + 400999^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-645736945877 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 645736945877.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (645736945871) 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, 44979374 + ... + 44993727.

It is an arithmetic number, because the mean of its divisors is an integer number (161456731539).

Almost surely, 2^645736945877 is an apocalyptic number.

It is an amenable number.

645736945877 is a deficient number, since it is larger than the sum of its proper divisors (89980279).

645736945877 is an equidigital number, since it uses as much as digits as its factorization.

645736945877 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 89980278.

The product of its digits is 1066867200, while the sum is 71.

The spelling of 645736945877 in words is "six hundred forty-five billion, seven hundred thirty-six million, nine hundred forty-five thousand, eight hundred seventy-seven".