643355549 has 2 divisors, whose sum is σ = 643355550. Its totient is φ = 643355548.

The previous prime is 643355521. The next prime is 643355567. The reversal of 643355549 is 945553346.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 525784900 + 117570649 = 22930^2 + 10843^2 .

It is a cyclic number.

It is not a de Polignac number, because 643355549 - 2²⁸ = 374920093 is a prime.

It is a Sophie Germain prime.

It is a Chen prime.

It is a Curzon number.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (643355509) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 321677774 + 321677775.

It is an arithmetic number, because the mean of its divisors is an integer number (321677775).

Almost surely, 2^643355549 is an apocalyptic number.

It is an amenable number.

643355549 is a deficient number, since it is larger than the sum of its proper divisors (1).

643355549 is an equidigital number, since it uses as much as digits as its factorization.

643355549 is an evil number, because the sum of its binary digits is even.

The product of its digits is 972000, while the sum is 44.

The square root of 643355549 is about 25364.4544392344. The cubic root of 643355549 is about 863.2773579519.

The spelling of 643355549 in words is "six hundred forty-three million, three hundred fifty-five thousand, five hundred forty-nine".