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20817 = 34257

20817 has 10 divisors (see below), whose sum is σ = 31218. Its totient is φ = 13824.

The previous prime is 20809. The next prime is 20849. The reversal of 20817 is 71802.

It can be written as a sum of positive squares in only one way, i.e., 20736 + 81 = 144^2 + 9^2 .

It is not a de Polignac number, because 20817 - 23 = 20809 is a prime.

20817 is an undulating number in base 16.

It is a plaindrome in base 7.

It is a self number, because there is not a number n which added to its sum of digits gives 20817.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20807) by changing a digit.

It is a polite number, since it can be written in 9 ways as a sum of consecutive naturals, for example, 48 + ... + 209.

220817 is an apocalyptic number.

20817 is a gapful number since it is divisible by the number (27) formed by its first and last digit.

It is an amenable number.

20817 is a deficient number, since it is larger than the sum of its proper divisors (10401).

20817 is an equidigital number, since it uses as much as digits as its factorization.

20817 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 269 (or 260 counting only the distinct ones).

The product of its (nonzero) digits is 112, while the sum is 18.

The square root of 20817 is about 144.2809758769. The cubic root of 20817 is about 27.5088676636.

It can be divided in two parts, 208 and 17, that added together give a square (225 = 152).

The spelling of 20817 in words is "twenty thousand, eight hundred seventeen".

Divisors: 1 3 9 27 81 257 771 2313 6939 20817