644782843 has 4 divisors (see below), whose sum is σ = 645670480. Its totient is φ = 643895208.

The previous prime is 644782819. The next prime is 644782861. The reversal of 644782843 is 348287446.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 644782843 - 2²⁵ = 611228411 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 644782793 and 644782802.

It is not an unprimeable number, because it can be changed into a prime (644782343) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 442728 + ... + 444181.

It is an arithmetic number, because the mean of its divisors is an integer number (161417620).

Almost surely, 2^644782843 is an apocalyptic number.

644782843 is a deficient number, since it is larger than the sum of its proper divisors (887637).

644782843 is an equidigital number, since it uses as much as digits as its factorization.

644782843 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 887636.

The product of its digits is 1032192, while the sum is 46.

The square root of 644782843 is about 25392.5745642304. The cubic root of 644782843 is about 863.9152843858.

The spelling of 644782843 in words is "six hundred forty-four million, seven hundred eighty-two thousand, eight hundred forty-three".