665819645 has 4 divisors (see below), whose sum is σ = 798983580. Its totient is φ = 532655712.

The previous prime is 665819597. The next prime is 665819681. The reversal of 665819645 is 546918566.

It is a happy number.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 502925476 + 162894169 = 22426^2 + 12763^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-665819645 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 665819593 and 665819602.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 66581960 + ... + 66581969.

It is an arithmetic number, because the mean of its divisors is an integer number (199745895).

Almost surely, 2^665819645 is an apocalyptic number.

It is an amenable number.

665819645 is a deficient number, since it is larger than the sum of its proper divisors (133163935).

665819645 is a wasteful number, since it uses less digits than its factorization.

665819645 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 133163934.

The product of its digits is 1555200, while the sum is 50.

The square root of 665819645 is about 25803.4812573808. The cubic root of 665819645 is about 873.2103371484.

The spelling of 665819645 in words is "six hundred sixty-five million, eight hundred nineteen thousand, six hundred forty-five".