201691 has 4 divisors (see below), whose sum is σ = 230512. Its totient is φ = 172872.

The previous prime is 201683. The next prime is 201701. The reversal of 201691 is 196102.

It is a semiprime because it is the product of two primes.

It is not a de Polignac number, because 201691 - 2³ = 201683 is a prime.

It is a Duffinian number.

It is a nialpdrome in base 12.

It is not an unprimeable number, because it can be changed into a prime (201611) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 14400 + ... + 14413.

It is an arithmetic number, because the mean of its divisors is an integer number (57628).

2²⁰¹⁶⁹¹ is an apocalyptic number.

201691 is a deficient number, since it is larger than the sum of its proper divisors (28821).

201691 is an equidigital number, since it uses as much as digits as its factorization.

201691 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 28820.

The product of its (nonzero) digits is 108, while the sum is 19.

The square root of 201691 is about 449.1002115341. The cubic root of 201691 is about 58.6447095575.

Adding to 201691 its reverse (196102), we get a palindrome (397793).

It can be divided in two parts, 20 and 1691, that added together give a triangular number (1711 = T₅₈).

The spelling of 201691 in words is "two hundred one thousand, six hundred ninety-one".