16171991 has 8 divisors (see below), whose sum is σ = 17906304. Its totient is φ = 14481720.

The previous prime is 16171973. The next prime is 16172017. The reversal of 16171991 is 19917161.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 16171991 - 2¹⁸ = 15909847 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (16171931) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 10235 + ... + 11708.

It is an arithmetic number, because the mean of its divisors is an integer number (2238288).

Almost surely, 2^16171991 is an apocalyptic number.

16171991 is a gapful number since it is divisible by the number (11) formed by its first and last digit.

16171991 is a deficient number, since it is larger than the sum of its proper divisors (1734313).

16171991 is a wasteful number, since it uses less digits than its factorization.

16171991 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 22021.

The product of its digits is 3402, while the sum is 35.

The square root of 16171991 is about 4021.4414082515. The cubic root of 16171991 is about 252.8838901254.

The spelling of 16171991 in words is "sixteen million, one hundred seventy-one thousand, nine hundred ninety-one".