645717 has 4 divisors (see below), whose sum is σ = 860960. Its totient is φ = 430476.

The previous prime is 645713. The next prime is 645727. The reversal of 645717 is 717546.

It is a happy number.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is not a de Polignac number, because 645717 - 2² = 645713 is a prime.

It is a D-number.

It is a Duffinian number.

It is a congruent number.

It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 645717.

It is not an unprimeable number, because it can be changed into a prime (645713) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 107617 + ... + 107622.

It is an arithmetic number, because the mean of its divisors is an integer number (215240).

2⁶⁴⁵⁷¹⁷ is an apocalyptic number.

It is an amenable number.

645717 is a deficient number, since it is larger than the sum of its proper divisors (215243).

645717 is a wasteful number, since it uses less digits than its factorization.

645717 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 215242.

The product of its digits is 5880, while the sum is 30.

The square root of 645717 is about 803.5651809281. The cubic root of 645717 is about 86.4332294594.

The spelling of 645717 in words is "six hundred forty-five thousand, seven hundred seventeen".