199751221 has 4 divisors (see below), whose sum is σ = 204623244. Its totient is φ = 194879200.

The previous prime is 199751219. The next prime is 199751231. The reversal of 199751221 is 122157991.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 122157991 = 23 ⋅5311217.

It can be written as a sum of positive squares in 2 ways, for example, as 20566225 + 179184996 = 4535^2 + 13386^2 .

It is a cyclic number.

It is not a de Polignac number, because 199751221 - 2¹ = 199751219 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 (199751231) 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 in 3 ways as a sum of consecutive naturals, for example, 2435950 + ... + 2436031.

It is an arithmetic number, because the mean of its divisors is an integer number (51155811).

Almost surely, 2^199751221 is an apocalyptic number.

It is an amenable number.

199751221 is a deficient number, since it is larger than the sum of its proper divisors (4872023).

199751221 is an equidigital number, since it uses as much as digits as its factorization.

199751221 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4872022.

The product of its digits is 11340, while the sum is 37.

The square root of 199751221 is about 14133.3372209114. The cubic root of 199751221 is about 584.5609689643.

The spelling of 199751221 in words is "one hundred ninety-nine million, seven hundred fifty-one thousand, two hundred twenty-one".