643897847 has 2 divisors, whose sum is σ = 643897848. Its totient is φ = 643897846.

The previous prime is 643897799. The next prime is 643897861. The reversal of 643897847 is 748798346.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 643897847 - 2¹⁰ = 643896823 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 643897792 and 643897801.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (643897447) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 321948923 + 321948924.

It is an arithmetic number, because the mean of its divisors is an integer number (321948924).

Almost surely, 2^643897847 is an apocalyptic number.

643897847 is a deficient number, since it is larger than the sum of its proper divisors (1).

643897847 is an equidigital number, since it uses as much as digits as its factorization.

643897847 is an evil number, because the sum of its binary digits is even.

The product of its digits is 8128512, while the sum is 56.

The square root of 643897847 is about 25375.1423050197. The cubic root of 643897847 is about 863.5198480795.

The spelling of 643897847 in words is "six hundred forty-three million, eight hundred ninety-seven thousand, eight hundred forty-seven".