645869 has 10 divisors (see below), whose sum is σ = 756270. Its totient is φ = 551544.

The previous prime is 645857. The next prime is 645877. The reversal of 645869 is 968546.

It can be written as a sum of positive squares in only one way, i.e., 405769 + 240100 = 637^2 + 490^2 .

It is a de Polignac number, because none of the positive numbers 2^k-645869 is a prime.

It is a super-2 number, since 2×645869² = 834293530322, which contains 22 as substring.

It is a Duffinian number.

It is a nialpdrome in base 7.

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 645869.

It is not an unprimeable number, because it can be changed into a prime (645839) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 9 ways as a sum of consecutive naturals, for example, 2267 + ... + 2535.

It is an arithmetic number, because the mean of its divisors is an integer number (75627).

2⁶⁴⁵⁸⁶⁹ is an apocalyptic number.

It is an amenable number.

645869 is a deficient number, since it is larger than the sum of its proper divisors (110401).

645869 is an frugal number, since it uses more digits than its factorization.

645869 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 297 (or 276 counting only the distinct ones).

The product of its digits is 51840, while the sum is 38.

The square root of 645869 is about 803.6597538760. The cubic root of 645869 is about 86.4400109752.

The spelling of 645869 in words is "six hundred forty-five thousand, eight hundred sixty-nine".