199961981 has 2 divisors, whose sum is σ = 199961982. Its totient is φ = 199961980.

The previous prime is 199961933. The next prime is 199962029. The reversal of 199961981 is 189169991.

It is a balanced prime because it is at equal distance from previous prime (199961933) and next prime (199962029).

It can be written as a sum of positive squares in only one way, i.e., 116532025 + 83429956 = 10795^2 + 9134^2 .

It is an emirp because it is prime and its reverse (189169991) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 199961981 - 2¹⁴ = 199945597 is a prime.

It is a super-2 number, since 2×199961981² = 79969587690888722, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (199961581) 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, 99980990 + 99980991.

It is an arithmetic number, because the mean of its divisors is an integer number (99980991).

Almost surely, 2^199961981 is an apocalyptic number.

It is an amenable number.

199961981 is a deficient number, since it is larger than the sum of its proper divisors (1).

199961981 is an equidigital number, since it uses as much as digits as its factorization.

199961981 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 314928, while the sum is 53.

The square root of 199961981 is about 14140.7913852090. The cubic root of 199961981 is about 584.7664892175.

The spelling of 199961981 in words is "one hundred ninety-nine million, nine hundred sixty-one thousand, nine hundred eighty-one".