8171991 has 6 divisors (see below), whose sum is σ = 11804000. Its totient is φ = 5447988.

The previous prime is 8171983. The next prime is 8171993. The reversal of 8171991 is 1991718.

It is not a de Polignac number, because 8171991 - 2³ = 8171983 is a prime.

It is a Duffinian number.

8171991 is a lucky number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (8171993) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 453991 + ... + 454008.

Almost surely, 2^8171991 is an apocalyptic number.

8171991 is a deficient number, since it is larger than the sum of its proper divisors (3632009).

8171991 is a wasteful number, since it uses less digits than its factorization.

8171991 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 908005 (or 908002 counting only the distinct ones).

The product of its digits is 4536, while the sum is 36.

The square root of 8171991 is about 2858.6694457387. The cubic root of 8171991 is about 201.4231081318.

It can be divided in two parts, 81719 and 91, that added together give a triangular number (81810 = T₄₀₄).

The spelling of 8171991 in words is "eight million, one hundred seventy-one thousand, nine hundred ninety-one".