199121821 has 2 divisors, whose sum is σ = 199121822. Its totient is φ = 199121820.

The previous prime is 199121807. The next prime is 199121851. The reversal of 199121821 is 128121991.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 148498596 + 50623225 = 12186^2 + 7115^2 .

It is an emirp because it is prime and its reverse (128121991) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 199121821 - 2⁷ = 199121693 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (199121851) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 99560910 + 99560911.

It is an arithmetic number, because the mean of its divisors is an integer number (99560911).

Almost surely, 2^199121821 is an apocalyptic number.

It is an amenable number.

199121821 is a deficient number, since it is larger than the sum of its proper divisors (1).

199121821 is an equidigital number, since it uses as much as digits as its factorization.

199121821 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 2592, while the sum is 34.

The square root of 199121821 is about 14111.0531499247. The cubic root of 199121821 is about 583.9463548100.

The spelling of 199121821 in words is "one hundred ninety-nine million, one hundred twenty-one thousand, eight hundred twenty-one".