643678109 has 2 divisors, whose sum is σ = 643678110. Its totient is φ = 643678108.

The previous prime is 643678103. The next prime is 643678121. The reversal of 643678109 is 901876346.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 643636900 + 41209 = 25370^2 + 203^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-643678109 is a prime.

It is a Sophie Germain prime.

It is a Chen prime.

It is a Curzon number.

It is a self number, because there is not a number n which added to its sum of digits gives 643678109.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (643678103) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 321839054 + 321839055.

It is an arithmetic number, because the mean of its divisors is an integer number (321839055).

Almost surely, 2^643678109 is an apocalyptic number.

It is an amenable number.

643678109 is a deficient number, since it is larger than the sum of its proper divisors (1).

643678109 is an equidigital number, since it uses as much as digits as its factorization.

643678109 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 217728, while the sum is 44.

The square root of 643678109 is about 25370.8121470323. The cubic root of 643678109 is about 863.4216080072.

The spelling of 643678109 in words is "six hundred forty-three million, six hundred seventy-eight thousand, one hundred nine".