643661371 has 8 divisors (see below), whose sum is σ = 672043680. Its totient is φ = 615312192.

The previous prime is 643661357. The next prime is 643661377. The reversal of 643661371 is 173166346.

It is a happy number.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 643661371 - 2¹⁷ = 643530299 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 643661371.

It is not an unprimeable number, because it can be changed into a prime (643661377) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 36685 + ... + 51313.

It is an arithmetic number, because the mean of its divisors is an integer number (84005460).

Almost surely, 2^643661371 is an apocalyptic number.

643661371 is a deficient number, since it is larger than the sum of its proper divisors (28382309).

643661371 is a wasteful number, since it uses less digits than its factorization.

643661371 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 16565.

The product of its digits is 54432, while the sum is 37.

The square root of 643661371 is about 25370.4822776391. The cubic root of 643661371 is about 863.4141238957.

The spelling of 643661371 in words is "six hundred forty-three million, six hundred sixty-one thousand, three hundred seventy-one".