644823847 has 2 divisors, whose sum is σ = 644823848. Its totient is φ = 644823846.

The previous prime is 644823797. The next prime is 644823857. The reversal of 644823847 is 748328446.

It is a strong prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-644823847 is a prime.

It is a Chen prime.

It is a junction number, because it is equal to n+sod(n) for n = 644823797 and 644823806.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (644823857) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 322411923 + 322411924.

It is an arithmetic number, because the mean of its divisors is an integer number (322411924).

Almost surely, 2^644823847 is an apocalyptic number.

644823847 is a deficient number, since it is larger than the sum of its proper divisors (1).

644823847 is an equidigital number, since it uses as much as digits as its factorization.

644823847 is an evil number, because the sum of its binary digits is even.

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

The square root of 644823847 is about 25393.3819527845. The cubic root of 644823847 is about 863.9335971308.

The spelling of 644823847 in words is "six hundred forty-four million, eight hundred twenty-three thousand, eight hundred forty-seven".