644867243 has 2 divisors, whose sum is σ = 644867244. Its totient is φ = 644867242.

The previous prime is 644867221. The next prime is 644867263. The reversal of 644867243 is 342768446.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 644867243 - 2⁸ = 644866987 is a prime.

It is a super-2 number, since 2×644867243² = 831707522188842098, which contains 22 as substring.

It is a junction number, because it is equal to n+sod(n) for n = 644867194 and 644867203.

It is not a weakly prime, because it can be changed into another prime (644867203) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 322433621 + 322433622.

It is an arithmetic number, because the mean of its divisors is an integer number (322433622).

Almost surely, 2^644867243 is an apocalyptic number.

644867243 is a deficient number, since it is larger than the sum of its proper divisors (1).

644867243 is an equidigital number, since it uses as much as digits as its factorization.

644867243 is an evil number, because the sum of its binary digits is even.

The product of its digits is 774144, while the sum is 44.

The square root of 644867243 is about 25394.2364130131. The cubic root of 644867243 is about 863.9529773184.

The spelling of 644867243 in words is "six hundred forty-four million, eight hundred sixty-seven thousand, two hundred forty-three".