644971273 has 2 divisors, whose sum is σ = 644971274. Its totient is φ = 644971272.

The previous prime is 644971219. The next prime is 644971289. The reversal of 644971273 is 372179446.

644971273 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 503194624 + 141776649 = 22432^2 + 11907^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-644971273 is a prime.

It is not a weakly prime, because it can be changed into another prime (644971073) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 322485636 + 322485637.

It is an arithmetic number, because the mean of its divisors is an integer number (322485637).

Almost surely, 2^644971273 is an apocalyptic number.

It is an amenable number.

644971273 is a deficient number, since it is larger than the sum of its proper divisors (1).

644971273 is an equidigital number, since it uses as much as digits as its factorization.

644971273 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 254016, while the sum is 43.

The square root of 644971273 is about 25396.2846298430. The cubic root of 644971273 is about 863.9994324592. Note that the first 3 decimals are identical.

The spelling of 644971273 in words is "six hundred forty-four million, nine hundred seventy-one thousand, two hundred seventy-three".