645865 has 8 divisors (see below), whose sum is σ = 845568. Its totient is φ = 469680.

The previous prime is 645857. The next prime is 645877. The reversal of 645865 is 568546.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 645865 - 2³ = 645857 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 645865.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 5817 + ... + 5926.

It is an arithmetic number, because the mean of its divisors is an integer number (105696).

2⁶⁴⁵⁸⁶⁵ is an apocalyptic number.

It is an amenable number.

645865 is a deficient number, since it is larger than the sum of its proper divisors (199703).

645865 is a wasteful number, since it uses less digits than its factorization.

645865 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 11759.

The product of its digits is 28800, while the sum is 34.

The square root of 645865 is about 803.6572652568. The cubic root of 645865 is about 86.4398325279.

It can be divided in two parts, 64 and 5865, that added together give a square (5929 = 77²).

The spelling of 645865 in words is "six hundred forty-five thousand, eight hundred sixty-five".