643989197 has 4 divisors (see below), whose sum is σ = 644921856. Its totient is φ = 643056540.

The previous prime is 643989191. The next prime is 643989221. The reversal of 643989197 is 791989346.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4, and also an emirpimes, since its reverse is a distinct semiprime: 791989346 = 2 ⋅395994673.

It is a cyclic number.

It is not a de Polignac number, because 643989197 - 2¹² = 643985101 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (643989191) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 465293 + ... + 466674.

It is an arithmetic number, because the mean of its divisors is an integer number (161230464).

Almost surely, 2^643989197 is an apocalyptic number.

It is an amenable number.

643989197 is a deficient number, since it is larger than the sum of its proper divisors (932659).

643989197 is an equidigital number, since it uses as much as digits as its factorization.

643989197 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 932658.

The product of its digits is 2939328, while the sum is 56.

The square root of 643989197 is about 25376.9422310884. The cubic root of 643989197 is about 863.5606820971.

The spelling of 643989197 in words is "six hundred forty-three million, nine hundred eighty-nine thousand, one hundred ninety-seven".