20001 has 8 divisors (see below), whose sum is σ = 27360.
Its totient is φ = 12992.
The previous prime is 19997. The next prime is 20011. The reversal of 20001 is 10002.
Adding to 20001 its reverse (10002), we get a palindrome (30003).
Subtracting from 20001 its reverse (10002), we obtain a palindrome (9999).
Multipling 20001 by its reverse (10002), we get a palindrome (200050002).
It is a sphenic number, since it is the product of 3 distinct primes.
It is a cyclic number.
It is not a de Polignac number, because 20001 - 22 = 19997 is a prime.
It is a Harshad number since it is a multiple of its sum of digits (3).
It is a congruent number.
It is not an unprimeable number, because it can be changed into a prime (20011) by changing a digit.
It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 121 + ... + 233.
It is an arithmetic number, because the mean of its divisors is an integer number (3420).
220001 is an apocalyptic number.
It is an amenable number.
20001 is a deficient number, since it is larger than the sum of its proper divisors (7359).
20001 is a wasteful number, since it uses less digits than its factorization.
20001 is an evil number, because the sum of its binary digits is even.
The sum of its prime factors is 175.
The product of its (nonzero) digits is 2, while the sum is 3.
The square root of 20001 is about 141.4248917270.
The cubic root of 20001 is about 27.1446285613.
The spelling of 20001 in words is "twenty thousand, one", and thus it is an iban number.