991749181 has 2 divisors, whose sum is σ = 991749182. Its totient is φ = 991749180.

The previous prime is 991749149. The next prime is 991749191. The reversal of 991749181 is 181947199.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 623301156 + 368448025 = 24966^2 + 19195^2 .

It is a cyclic number.

It is not a de Polignac number, because 991749181 - 2⁵ = 991749149 is a prime.

It is a super-2 number, since 2×991749181² = 1967132876028341522, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (991749191) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 495874590 + 495874591.

It is an arithmetic number, because the mean of its divisors is an integer number (495874591).

Almost surely, 2^991749181 is an apocalyptic number.

It is an amenable number.

991749181 is a deficient number, since it is larger than the sum of its proper divisors (1).

991749181 is an equidigital number, since it uses as much as digits as its factorization.

991749181 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 163296, while the sum is 49.

The square root of 991749181 is about 31492.0494887202. The cubic root of 991749181 is about 997.2421281348.

The spelling of 991749181 in words is "nine hundred ninety-one million, seven hundred forty-nine thousand, one hundred eighty-one".