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20081 = 43467
BaseRepresentation
bin100111001110001
31000112202
410321301
51120311
6232545
7112355
oct47161
930482
1020081
11140a6
12b755
1391a9
147465
155e3b
hex4e71

20081 has 4 divisors (see below), whose sum is σ = 20592. Its totient is φ = 19572.

The previous prime is 20071. The next prime is 20089. The reversal of 20081 is 18002.

Adding to 20081 its reverse (18002), we get a palindrome (38083).

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4, and also an emirpimes, since its reverse is a distinct semiprime: 18002 = 29001.

It is a cyclic number.

It is not a de Polignac number, because 20081 - 214 = 3697 is a prime.

It is a super-2 number, since 2×200812 = 806493122, which contains 22 as substring.

It is a Duffinian number.

It is a Curzon number.

It is a plaindrome in base 7.

It is a nialpdrome in base 12.

It is not an unprimeable number, because it can be changed into a prime (20089) 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, 191 + ... + 276.

It is an arithmetic number, because the mean of its divisors is an integer number (5148).

220081 is an apocalyptic number.

It is an amenable number.

20081 is a deficient number, since it is larger than the sum of its proper divisors (511).

20081 is an equidigital number, since it uses as much as digits as its factorization.

20081 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 510.

The product of its (nonzero) digits is 16, while the sum is 11.

The square root of 20081 is about 141.7074451114. The cubic root of 20081 is about 27.1807714445.

The spelling of 20081 in words is "twenty thousand, eighty-one".

Divisors: 1 43 467 20081