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20689 = 171217
BaseRepresentation
bin101000011010001
31001101021
411003101
51130224
6235441
7114214
oct50321
931337
1020689
11145a9
12bb81
139556
14777b
1561e4
hex50d1

20689 has 4 divisors (see below), whose sum is σ = 21924. Its totient is φ = 19456.

The previous prime is 20681. The next prime is 20693. The reversal of 20689 is 98602.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 11664 + 9025 = 108^2 + 95^2 .

It is a cyclic number.

It is not a de Polignac number, because 20689 - 23 = 20681 is a prime.

It is a Duffinian number.

It is a plaindrome in base 14.

It is a nialpdrome in base 12.

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, 592 + ... + 625.

It is an arithmetic number, because the mean of its divisors is an integer number (5481).

220689 is an apocalyptic number.

It is an amenable number.

20689 is a deficient number, since it is larger than the sum of its proper divisors (1235).

20689 is a wasteful number, since it uses less digits than its factorization.

20689 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1234.

The product of its (nonzero) digits is 864, while the sum is 25.

The square root of 20689 is about 143.8367129769. The cubic root of 20689 is about 27.4523693408.

The spelling of 20689 in words is "twenty thousand, six hundred eighty-nine".

Divisors: 1 17 1217 20689