991606171 has 2 divisors, whose sum is σ = 991606172. Its totient is φ = 991606170.

The previous prime is 991606169. The next prime is 991606211. The reversal of 991606171 is 171606199.

It is an a-pointer prime, because the next prime (991606211) can be obtained adding 991606171 to its sum of digits (40).

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 991606171 - 2¹ = 991606169 is a prime.

Together with 991606169, it forms a pair of twin primes.

It is not a weakly prime, because it can be changed into another prime (991606111) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 495803085 + 495803086.

It is an arithmetic number, because the mean of its divisors is an integer number (495803086).

Almost surely, 2^991606171 is an apocalyptic number.

991606171 is a deficient number, since it is larger than the sum of its proper divisors (1).

991606171 is an equidigital number, since it uses as much as digits as its factorization.

991606171 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 20412, while the sum is 40.

The square root of 991606171 is about 31489.7788337740. The cubic root of 991606171 is about 997.1941918033.

The spelling of 991606171 in words is "nine hundred ninety-one million, six hundred six thousand, one hundred seventy-one".