643849 has 2 divisors, whose sum is σ = 643850. Its totient is φ = 643848.

The previous prime is 643847. The next prime is 643859. The reversal of 643849 is 948346.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 413449 + 230400 = 643^2 + 480^2 .

It is a cyclic number.

It is not a de Polignac number, because 643849 - 2¹ = 643847 is a prime.

Together with 643847, it forms a pair of twin primes.

It is not a weakly prime, because it can be changed into another prime (643847) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 321924 + 321925.

It is an arithmetic number, because the mean of its divisors is an integer number (321925).

2⁶⁴³⁸⁴⁹ is an apocalyptic number.

It is an amenable number.

643849 is a deficient number, since it is larger than the sum of its proper divisors (1).

643849 is an equidigital number, since it uses as much as digits as its factorization.

643849 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 20736, while the sum is 34.

The square root of 643849 is about 802.4020189406. The cubic root of 643849 is about 86.3498011582.

The spelling of 643849 in words is "six hundred forty-three thousand, eight hundred forty-nine".