645805889 has 4 divisors (see below), whose sum is σ = 645872724. Its totient is φ = 645739056.

The previous prime is 645805873. The next prime is 645805903. The reversal of 645805889 is 988508546.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length.

It can be written as a sum of positive squares in 2 ways, for example, as 291726400 + 354079489 = 17080^2 + 18817^2 .

It is a cyclic number.

It is not a de Polignac number, because 645805889 - 2⁴ = 645805873 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 645805889.

It is not an unprimeable number, because it can be changed into a prime (645805789) 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, 15842 + ... + 39275.

It is an arithmetic number, because the mean of its divisors is an integer number (161468181).

Almost surely, 2^645805889 is an apocalyptic number.

It is an amenable number.

645805889 is a deficient number, since it is larger than the sum of its proper divisors (66835).

645805889 is a wasteful number, since it uses less digits than its factorization.

645805889 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 66834.

The product of its (nonzero) digits is 2764800, while the sum is 53.

The square root of 645805889 is about 25412.7111698063. The cubic root of 645805889 is about 864.3719539225.

The spelling of 645805889 in words is "six hundred forty-five million, eight hundred five thousand, eight hundred eighty-nine".