20687 has 4 divisors (see below), whose sum is σ = 20976. Its totient is φ = 20400.

The previous prime is 20681. The next prime is 20693. The reversal of 20687 is 78602.

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: 78602 = 2 ⋅39301.

It is an interprime number because it is at equal distance from previous prime (20681) and next prime (20693).

It is a cyclic number.

It is not a de Polignac number, because 20687 - 2⁸ = 20431 is a prime.

It is a Duffinian number.

It is a plaindrome in base 14.

It is a nialpdrome in base 13.

It is a congruent number.

It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 20687.

It is not an unprimeable number, because it can be changed into a prime (20681) 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, 62 + ... + 212.

It is an arithmetic number, because the mean of its divisors is an integer number (5244).

2²⁰⁶⁸⁷ is an apocalyptic number.

20687 is a deficient number, since it is larger than the sum of its proper divisors (289).

20687 is a wasteful number, since it uses less digits than its factorization.

20687 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 288.

The product of its (nonzero) digits is 672, while the sum is 23.

The square root of 20687 is about 143.8297604809. The cubic root of 20687 is about 27.4514847080.

It can be divided in two parts, 20 and 687, that added together give a palindrome (707).

The spelling of 20687 in words is "twenty thousand, six hundred eighty-seven".