643544591 has 2 divisors, whose sum is σ = 643544592. Its totient is φ = 643544590.

The previous prime is 643544549. The next prime is 643544599. The reversal of 643544591 is 195445346.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 643544591 - 2⁶ = 643544527 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (643544599) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 321772295 + 321772296.

It is an arithmetic number, because the mean of its divisors is an integer number (321772296).

Almost surely, 2^643544591 is an apocalyptic number.

643544591 is a deficient number, since it is larger than the sum of its proper divisors (1).

643544591 is an equidigital number, since it uses as much as digits as its factorization.

643544591 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 259200, while the sum is 41.

The square root of 643544591 is about 25368.1806797413. The cubic root of 643544591 is about 863.3619040980.

The spelling of 643544591 in words is "six hundred forty-three million, five hundred forty-four thousand, five hundred ninety-one".