643799641 has 2 divisors, whose sum is σ = 643799642. Its totient is φ = 643799640.

The previous prime is 643799627. The next prime is 643799657. The reversal of 643799641 is 146997346.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 559086025 + 84713616 = 23645^2 + 9204^2 .

It is a cyclic number.

It is not a de Polignac number, because 643799641 - 2²³ = 635411033 is a prime.

It is not a weakly prime, because it can be changed into another prime (643799621) 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, 321899820 + 321899821.

It is an arithmetic number, because the mean of its divisors is an integer number (321899821).

Almost surely, 2^643799641 is an apocalyptic number.

It is an amenable number.

643799641 is a deficient number, since it is larger than the sum of its proper divisors (1).

643799641 is an equidigital number, since it uses as much as digits as its factorization.

643799641 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 979776, while the sum is 49.

The square root of 643799641 is about 25373.2071484864. The cubic root of 643799641 is about 863.4759450793.

The spelling of 643799641 in words is "six hundred forty-three million, seven hundred ninety-nine thousand, six hundred forty-one".