20311 has 4 divisors (see below), whose sum is σ = 21400. Its totient is φ = 19224.

The previous prime is 20297. The next prime is 20323. The reversal of 20311 is 11302.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 11302 = 2 ⋅5651.

It is a cyclic number.

It is not a de Polignac number, because 20311 - 2⁷ = 20183 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 20294 and 20303.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20341) 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, 516 + ... + 553.

It is an arithmetic number, because the mean of its divisors is an integer number (5350).

2²⁰³¹¹ is an apocalyptic number.

20311 is a deficient number, since it is larger than the sum of its proper divisors (1089).

20311 is a wasteful number, since it uses less digits than its factorization.

20311 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1088.

The product of its (nonzero) digits is 6, while the sum is 7.

The square root of 20311 is about 142.5166656921. The cubic root of 20311 is about 27.2841504336.

Adding to 20311 its reverse (11302), we get a palindrome (31613).

Subtracting from 20311 its reverse (11302), we obtain a palindrome (9009).

The spelling of 20311 in words is "twenty thousand, three hundred eleven", and thus it is an iban number.