644977843 has 2 divisors, whose sum is σ = 644977844. Its totient is φ = 644977842.

The previous prime is 644977831. The next prime is 644977873. The reversal of 644977843 is 348779446.

644977843 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 644977843 - 2²⁹ = 108106931 is a prime.

It is not a weakly prime, because it can be changed into another prime (644977873) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 322488921 + 322488922.

It is an arithmetic number, because the mean of its divisors is an integer number (322488922).

Almost surely, 2^644977843 is an apocalyptic number.

644977843 is a deficient number, since it is larger than the sum of its proper divisors (1).

644977843 is an equidigital number, since it uses as much as digits as its factorization.

644977843 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 4064256, while the sum is 52.

The square root of 644977843 is about 25396.4139791428. The cubic root of 644977843 is about 864.0023661594.

The spelling of 644977843 in words is "six hundred forty-four million, nine hundred seventy-seven thousand, eight hundred forty-three".