643847 has 2 divisors, whose sum is σ = 643848. Its totient is φ = 643846.

The previous prime is 643781. The next prime is 643849. The reversal of 643847 is 748346.

It is a happy number.

643847 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 643847 - 2¹⁶ = 578311 is a prime.

Together with 643849, it forms a pair of twin primes.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (643849) by changing a digit.

It is a good prime.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 321923 + 321924.

It is an arithmetic number, because the mean of its divisors is an integer number (321924).

2⁶⁴³⁸⁴⁷ is an apocalyptic number.

643847 is a deficient number, since it is larger than the sum of its proper divisors (1).

643847 is an equidigital number, since it uses as much as digits as its factorization.

643847 is an evil number, because the sum of its binary digits is even.

The product of its digits is 16128, while the sum is 32.

The square root of 643847 is about 802.4007726816. The cubic root of 643847 is about 86.3497117481.

The spelling of 643847 in words is "six hundred forty-three thousand, eight hundred forty-seven".