20105 has 4 divisors (see below), whose sum is σ = 24132. Its totient is φ = 16080.

The previous prime is 20101. The next prime is 20107. The reversal of 20105 is 50102.

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 3721 + 16384 = 61^2 + 128^2 .

It is not a de Polignac number, because 20105 - 2² = 20101 is a prime.

It is a super-2 number, since 2×20105² = 808422050, which contains 22 as substring.

It is a Duffinian number.

It is a nialpdrome in base 12.

It is a junction number, because it is equal to n+sod(n) for n = 20092 and 20101.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20101) 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 3 ways as a sum of consecutive naturals, for example, 2006 + ... + 2015.

It is an arithmetic number, because the mean of its divisors is an integer number (6033).

2²⁰¹⁰⁵ is an apocalyptic number.

It is an amenable number.

20105 is a deficient number, since it is larger than the sum of its proper divisors (4027).

20105 is an equidigital number, since it uses as much as digits as its factorization.

20105 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4026.

The product of its (nonzero) digits is 10, while the sum is 8.

The square root of 20105 is about 141.7921013315. The cubic root of 20105 is about 27.1915955868.

Adding to 20105 its reverse (50102), we get a palindrome (70207).

It can be divided in two parts, 20 and 105, that added together give a cube (125 = 5³).

The spelling of 20105 in words is "twenty thousand, one hundred five".