• 201912 = 407676481 is an anagram of the next square 201922 = 407716864.
20191 has 4 divisors (see below), whose sum is σ = 20584. Its totient is φ = 19800.
The previous prime is 20183. The next prime is 20201. The reversal of 20191 is 19102.
It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 19102 = 2 ⋅9551.
It is a cyclic number.
It is not a de Polignac number, because 20191 - 23 = 20183 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 (20101) 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, 105 + ... + 226.
It is an arithmetic number, because the mean of its divisors is an integer number (5146).
220191 is an apocalyptic number.
20191 is a deficient number, since it is larger than the sum of its proper divisors (393).
20191 is an equidigital number, since it uses as much as digits as its factorization.
20191 is an odious number, because the sum of its binary digits is odd.
The sum of its prime factors is 392.
The product of its (nonzero) digits is 18, while the sum is 13.
The square root of 20191 is about 142.0950386185. The cubic root of 20191 is about 27.2303115084.
Adding to 20191 its reverse (19102), we get a palindrome (39293).
Subtracting from 20191 its reverse (19102), we obtain a square (1089 = 332).
It can be divided in two parts, 201 and 91, that added together give a palindrome (292).
The spelling of 20191 in words is "twenty thousand, one hundred ninety-one".
• e-mail: info -at- numbersaplenty.com • Privacy notice • done in 0.075 sec. • engine limits •