643749539 has 2 divisors, whose sum is σ = 643749540. Its totient is φ = 643749538.

The previous prime is 643749481. The next prime is 643749541. The reversal of 643749539 is 935947346.

It is a strong prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-643749539 is a prime.

It is a Sophie Germain prime.

Together with 643749541, it forms a pair of twin primes.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (643749739) 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, 321874769 + 321874770.

It is an arithmetic number, because the mean of its divisors is an integer number (321874770).

Almost surely, 2^643749539 is an apocalyptic number.

643749539 is a deficient number, since it is larger than the sum of its proper divisors (1).

643749539 is an equidigital number, since it uses as much as digits as its factorization.

643749539 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 2449440, while the sum is 50.

The square root of 643749539 is about 25372.2198279930. The cubic root of 643749539 is about 863.4535452563.

The spelling of 643749539 in words is "six hundred forty-three million, seven hundred forty-nine thousand, five hundred thirty-nine".