645865844 has 48 divisors (see below), whose sum is σ = 1283098320. Its totient is φ = 282347520.

The previous prime is 645865789. The next prime is 645865859. The reversal of 645865844 is 448568546.

It can be written as a sum of positive squares in 8 ways, for example, as 14348944 + 631516900 = 3788^2 + 25130^2 .

It is a junction number, because it is equal to n+sod(n) for n = 645865792 and 645865801.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 75884 + ... + 83964.

It is an arithmetic number, because the mean of its divisors is an integer number (26731215).

Almost surely, 2^645865844 is an apocalyptic number.

It is an amenable number.

645865844 is a deficient number, since it is larger than the sum of its proper divisors (637232476).

645865844 is a wasteful number, since it uses less digits than its factorization.

645865844 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 8180 (or 8178 counting only the distinct ones).

The product of its digits is 3686400, while the sum is 50.

The square root of 645865844 is about 25413.8907686328. The cubic root of 645865844 is about 864.3987018034.

The spelling of 645865844 in words is "six hundred forty-five million, eight hundred sixty-five thousand, eight hundred forty-four".