643866847 has 12 divisors (see below), whose sum is σ = 697919544. Its totient is φ = 593729760.

The previous prime is 643866809. The next prime is 643866871. The reversal of 643866847 is 748668346.

It is a happy number.

It is not a de Polignac number, because 643866847 - 2⁷ = 643866719 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 643866794 and 643866803.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (643866877) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 325353 + ... + 327325.

It is an arithmetic number, because the mean of its divisors is an integer number (58159962).

Almost surely, 2^643866847 is an apocalyptic number.

643866847 is a deficient number, since it is larger than the sum of its proper divisors (54052697).

643866847 is a wasteful number, since it uses less digits than its factorization.

643866847 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3930 (or 3917 counting only the distinct ones).

The product of its digits is 4644864, while the sum is 52.

The square root of 643866847 is about 25374.5314636547. The cubic root of 643866847 is about 863.5059900092.

The spelling of 643866847 in words is "six hundred forty-three million, eight hundred sixty-six thousand, eight hundred forty-seven".