199188721 has 2 divisors, whose sum is σ = 199188722. Its totient is φ = 199188720.

The previous prime is 199188719. The next prime is 199188727. The reversal of 199188721 is 127881991.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 171479025 + 27709696 = 13095^2 + 5264^2 .

It is a cyclic number.

It is not a de Polignac number, because 199188721 - 2¹ = 199188719 is a prime.

It is a super-2 number, since 2×199188721² = 79352293147231682, which contains 22 as substring.

Together with 199188719, it forms a pair of twin primes.

It is not a weakly prime, because it can be changed into another prime (199188727) 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, 99594360 + 99594361.

It is an arithmetic number, because the mean of its divisors is an integer number (99594361).

Almost surely, 2^199188721 is an apocalyptic number.

It is an amenable number.

199188721 is a deficient number, since it is larger than the sum of its proper divisors (1).

199188721 is an equidigital number, since it uses as much as digits as its factorization.

199188721 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 72576, while the sum is 46.

The square root of 199188721 is about 14113.4234330300. The cubic root of 199188721 is about 584.0117446581.

The spelling of 199188721 in words is "one hundred ninety-nine million, one hundred eighty-eight thousand, seven hundred twenty-one".