645965 has 4 divisors (see below), whose sum is σ = 775164. Its totient is φ = 516768.

The previous prime is 645941. The next prime is 645973. The reversal of 645965 is 569546.

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 259081 + 386884 = 509^2 + 622^2 .

It is a cyclic number.

It is not a de Polignac number, because 645965 - 2⁶ = 645901 is a prime.

It is a Duffinian number.

It is a Curzon number.

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, 64592 + ... + 64601.

It is an arithmetic number, because the mean of its divisors is an integer number (193791).

2⁶⁴⁵⁹⁶⁵ is an apocalyptic number.

It is an amenable number.

645965 is a deficient number, since it is larger than the sum of its proper divisors (129199).

645965 is a wasteful number, since it uses less digits than its factorization.

645965 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 129198.

The product of its digits is 32400, while the sum is 35.

The square root of 645965 is about 803.7194784252. The cubic root of 645965 is about 86.4442934896. Note that the first 3 decimals are identical.

The spelling of 645965 in words is "six hundred forty-five thousand, nine hundred sixty-five".