199999781 has 4 divisors (see below), whose sum is σ = 211764492. Its totient is φ = 188235072.

The previous prime is 199999777. The next prime is 199999819. The reversal of 199999781 is 187999991.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 178756900 + 21242881 = 13370^2 + 4609^2 .

It is a cyclic number.

It is not a de Polignac number, because 199999781 - 2² = 199999777 is a prime.

It is a super-2 number, since 2×199999781² = 79999824800095922, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (199999721) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 5882330 + ... + 5882363.

It is an arithmetic number, because the mean of its divisors is an integer number (52941123).

Almost surely, 2^199999781 is an apocalyptic number.

It is an amenable number.

199999781 is a deficient number, since it is larger than the sum of its proper divisors (11764711).

199999781 is a wasteful number, since it uses less digits than its factorization.

199999781 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 11764710.

The product of its digits is 3306744, while the sum is 62.

The square root of 199999781 is about 14142.1278809096. The cubic root of 199999781 is about 584.8033341892.

The spelling of 199999781 in words is "one hundred ninety-nine million, nine hundred ninety-nine thousand, seven hundred eighty-one".