20101 has 2 divisors, whose sum is σ = 20102.
Its totient is φ = 20100.
The previous prime is 20089. The next prime is 20107. The reversal of 20101 is 10102.
Adding to 20101 its reverse (10102), we get a palindrome (30203).
Subtracting from 20101 its reverse (10102), we obtain a palindrome (9999).
Multipling 20101 by its reverse (10102), we get a palindrome (203060302).
It can be divided in two parts, 20 and 101, that added together give a palindrome (121).
It is a strong prime.
It can be written as a sum of positive squares in only one way, i.e., 15876 + 4225 = 126^2 + 65^2
It is a cyclic number.
It is not a de Polignac number, because 20101 - 27 = 19973 is a prime.
It is a Chen prime.
It is a pancake number, because a pancake can be divided into 20101 parts by 200 straight cuts.
20101 is a modest number, since divided by 101 gives 2 as remainder.
20101 is a lucky number.
It is a nialpdrome in base 12.
It is a congruent number.
It is not a weakly prime, because it can be changed into another prime (20107) 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 as a sum of consecutive naturals, namely, 10050 + 10051.
It is an arithmetic number, because the mean of its divisors is an integer number (10051).
220101 is an apocalyptic number.
It is an amenable number.
20101 is a deficient number, since it is larger than the sum of its proper divisors (1).
20101 is an equidigital number, since it uses as much as digits as its factorization.
20101 is an odious number, because the sum of its binary digits is odd.
The product of its (nonzero) digits is 2, while the sum is 4.
The square root of 20101 is about 141.7779954718.
Note that the first 3 decimals coincide.
The cubic root of 20101 is about 27.1897921615.
The spelling of 20101 in words is "twenty thousand, one hundred one", and thus it is an iban number.