645999 has 8 divisors (see below), whose sum is σ = 865200.
Its totient is φ = 428736.
The previous prime is 645979. The next prime is 646003. The reversal of 645999 is 999546.
It is a happy number.
It is a sphenic number, since it is the product of 3 distinct primes.
It is not a de Polignac number, because 645999 - 215 = 613231 is a prime.
645999 is a modest number, since divided by 999 gives 645 as remainder.
It is a plaindrome in base 8.
It is a self number, because there is not a number n which added to its sum of digits gives 645999.
It is a congruent number.
It is not an unprimeable number, because it can be changed into a prime (645979) by changing a digit.
It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 739 + ... + 1355.
It is an arithmetic number, because the mean of its divisors is an integer number (108150).
2645999 is an apocalyptic number.
645999 is a deficient number, since it is larger than the sum of its proper divisors (219201).
645999 is a wasteful number, since it uses less digits than its factorization.
645999 is an evil number, because the sum of its binary digits is even.
The sum of its prime factors is 969.
The product of its digits is 87480, while the sum is 42.
The square root of 645999 is about 803.7406298054.
The cubic root of 645999 is about 86.4458101118.
The spelling of 645999 in words is "six hundred forty-five thousand, nine hundred ninety-nine".