643975441 has 2 divisors, whose sum is σ = 643975442. Its totient is φ = 643975440.

The previous prime is 643975427. The next prime is 643975447. The reversal of 643975441 is 144579346.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 641153041 + 2822400 = 25321^2 + 1680^2 .

It is a cyclic number.

It is not a de Polignac number, because 643975441 - 2⁷ = 643975313 is a prime.

It is a super-2 number, since 2×643975441² = 829408737222288962, which contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (643975447) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 321987720 + 321987721.

It is an arithmetic number, because the mean of its divisors is an integer number (321987721).

Almost surely, 2^643975441 is an apocalyptic number.

It is an amenable number.

643975441 is a deficient number, since it is larger than the sum of its proper divisors (1).

643975441 is an equidigital number, since it uses as much as digits as its factorization.

643975441 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 362880, while the sum is 43.

The square root of 643975441 is about 25376.6711961991. The cubic root of 643975441 is about 863.5545333266.

The spelling of 643975441 in words is "six hundred forty-three million, nine hundred seventy-five thousand, four hundred forty-one".