20291 has 4 divisors (see below), whose sum is σ = 20592. Its totient is φ = 19992.

The previous prime is 20287. The next prime is 20297. The reversal of 20291 is 19202.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length, and also an emirpimes, since its reverse is a distinct semiprime: 19202 = 2 ⋅9601.

It is a cyclic number.

It is not a de Polignac number, because 20291 - 2² = 20287 is a prime.

It is a Duffinian number.

20291 is an undulating number in base 14.

It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 20291.

It is not an unprimeable number, because it can be changed into a prime (20297) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 5 + ... + 201.

It is an arithmetic number, because the mean of its divisors is an integer number (5148).

2²⁰²⁹¹ is an apocalyptic number.

20291 is a deficient number, since it is larger than the sum of its proper divisors (301).

20291 is a wasteful number, since it uses less digits than its factorization.

20291 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 300.

The product of its (nonzero) digits is 36, while the sum is 14.

The square root of 20291 is about 142.4464811780. The cubic root of 20291 is about 27.2751920331.

Adding to 20291 its reverse (19202), we get a palindrome (39493).

Subtracting from 20291 its reverse (19202), we obtain a square (1089 = 33²).

The spelling of 20291 in words is "twenty thousand, two hundred ninety-one".