20511 has 12 divisors (see below), whose sum is σ = 30888. Its totient is φ = 13104.

The previous prime is 20509. The next prime is 20521. The reversal of 20511 is 11502.

It is a happy number.

20511 is an esthetic number in base 6, because in such base its adjacent digits differ by 1.

It is not a de Polignac number, because 20511 - 2¹ = 20509 is a prime.

It is a super-2 number, since 2×20511² = 841402242, which contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (9).

20511 is a lucky number.

It is a plaindrome in base 11.

It is a nialpdrome in base 12.

It is a junction number, because it is equal to n+sod(n) for n = 20493 and 20502.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20521) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 361 + ... + 413.

It is an arithmetic number, because the mean of its divisors is an integer number (2574).

2²⁰⁵¹¹ is an apocalyptic number.

20511 is a deficient number, since it is larger than the sum of its proper divisors (10377).

20511 is a wasteful number, since it uses less digits than its factorization.

20511 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 102 (or 99 counting only the distinct ones).

The product of its (nonzero) digits is 10, while the sum is 9.

The square root of 20511 is about 143.2166191474. The cubic root of 20511 is about 27.3734126808.

Subtracting from 20511 its reverse (11502), we obtain a palindrome (9009).

It can be divided in two parts, 205 and 11, that added together give a cube (216 = 6³).

The spelling of 20511 in words is "twenty thousand, five hundred eleven".