643666347 has 6 divisors (see below), whose sum is σ = 929740292. Its totient is φ = 429110892.

The previous prime is 643666343. The next prime is 643666351. The reversal of 643666347 is 743666346.

It is an interprime number because it is at equal distance from previous prime (643666343) and next prime (643666351).

It is not a de Polignac number, because 643666347 - 2² = 643666343 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (643666343) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 35759233 + ... + 35759250.

Almost surely, 2^643666347 is an apocalyptic number.

643666347 is a deficient number, since it is larger than the sum of its proper divisors (286073945).

643666347 is a wasteful number, since it uses less digits than its factorization.

643666347 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 71518489 (or 71518486 counting only the distinct ones).

The product of its digits is 1306368, while the sum is 45.

The square root of 643666347 is about 25370.5803441703. The cubic root of 643666347 is about 863.4163488429.

Subtracting 643666347 from its reverse (743666346), we obtain a palindrome (99999999).

The spelling of 643666347 in words is "six hundred forty-three million, six hundred sixty-six thousand, three hundred forty-seven".