643905947 has 2 divisors, whose sum is σ = 643905948. Its totient is φ = 643905946.

The previous prime is 643905863. The next prime is 643905959. The reversal of 643905947 is 749509346.

It is a happy number.

643905947 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 643905947 - 2¹⁰ = 643904923 is a prime.

It is a super-2 number, since 2×643905947² = 829229737163933618, which contains 22 as substring.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (643905547) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 321952973 + 321952974.

It is an arithmetic number, because the mean of its divisors is an integer number (321952974).

Almost surely, 2^643905947 is an apocalyptic number.

643905947 is a deficient number, since it is larger than the sum of its proper divisors (1).

643905947 is an equidigital number, since it uses as much as digits as its factorization.

643905947 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 816480, while the sum is 47.

The square root of 643905947 is about 25375.3019095340. The cubic root of 643905947 is about 863.5234689858.

The spelling of 643905947 in words is "six hundred forty-three million, nine hundred five thousand, nine hundred forty-seven".