193991989 has 2 divisors, whose sum is σ = 193991990. Its totient is φ = 193991988.

The previous prime is 193991977. The next prime is 193992023. The reversal of 193991989 is 989199391.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 152324964 + 41667025 = 12342^2 + 6455^2 .

It is a cyclic number.

It is not a de Polignac number, because 193991989 - 2⁹ = 193991477 is a prime.

It is a super-2 number, since 2×193991989² = 75265783592352242, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (193991939) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 96995994 + 96995995.

It is an arithmetic number, because the mean of its divisors is an integer number (96995995).

Almost surely, 2^193991989 is an apocalyptic number.

It is an amenable number.

193991989 is a deficient number, since it is larger than the sum of its proper divisors (1).

193991989 is an equidigital number, since it uses as much as digits as its factorization.

193991989 is an evil number, because the sum of its binary digits is even.

The product of its digits is 1417176, while the sum is 58.

The square root of 193991989 is about 13928.1006960748. The cubic root of 193991989 is about 578.8880688214. Note that the first 3 decimals are identical.

The spelling of 193991989 in words is "one hundred ninety-three million, nine hundred ninety-one thousand, nine hundred eighty-nine".