645899 has 4 divisors (see below), whose sum is σ = 647520. Its totient is φ = 644280.

The previous prime is 645893. The next prime is 645901. The reversal of 645899 is 998546.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length.

It is a cyclic number.

It is not a de Polignac number, because 645899 - 2¹² = 641803 is a prime.

It is a Duffinian number.

Its product of digits (77760) is a multiple of the sum of its prime divisors (1620).

It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 645899.

It is not an unprimeable number, because it can be changed into a prime (645893) 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, 254 + ... + 1164.

It is an arithmetic number, because the mean of its divisors is an integer number (161880).

2⁶⁴⁵⁸⁹⁹ is an apocalyptic number.

645899 is a deficient number, since it is larger than the sum of its proper divisors (1621).

645899 is an equidigital number, since it uses as much as digits as its factorization.

645899 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1620.

The product of its digits is 77760, while the sum is 41.

The square root of 645899 is about 803.6784182744. The cubic root of 645899 is about 86.4413493065.

The spelling of 645899 in words is "six hundred forty-five thousand, eight hundred ninety-nine".