199878221 has 2 divisors, whose sum is σ = 199878222. Its totient is φ = 199878220.

The previous prime is 199878209. The next prime is 199878223. The reversal of 199878221 is 122878991.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 111724900 + 88153321 = 10570^2 + 9389^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-199878221 is a prime.

It is a Sophie Germain prime.

Together with 199878223, it forms a pair of twin primes.

It is a Chen prime.

It is a Curzon number.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (199878223) 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 as a sum of consecutive naturals, namely, 99939110 + 99939111.

It is an arithmetic number, because the mean of its divisors is an integer number (99939111).

Almost surely, 2^199878221 is an apocalyptic number.

It is an amenable number.

199878221 is a deficient number, since it is larger than the sum of its proper divisors (1).

199878221 is an equidigital number, since it uses as much as digits as its factorization.

199878221 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 145152, while the sum is 47.

The square root of 199878221 is about 14137.8294302909. The cubic root of 199878221 is about 584.6848288915.

The spelling of 199878221 in words is "one hundred ninety-nine million, eight hundred seventy-eight thousand, two hundred twenty-one".