20121 has 8 divisors (see below), whose sum is σ = 28320.
Its totient is φ = 12672.
The previous prime is 20117. The next prime is 20123. The reversal of 20121 is 12102.
Adding to 20121 its reverse (12102), we get a palindrome (32223).
It can be divided in two parts, 201 and 21, that added together give a palindrome (222).
20121 = T38 + T39 + ... +
It is a happy number.
It is a sphenic number, since it is the product of 3 distinct primes.
It is not a de Polignac number, because 20121 - 22 = 20117 is a prime.
20121 is a lucky number.
It is not an unprimeable number, because it can be changed into a prime (20123) 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, 120 + ... + 233.
It is an arithmetic number, because the mean of its divisors is an integer number (3540).
220121 is an apocalyptic number.
It is an amenable number.
20121 is a deficient number, since it is larger than the sum of its proper divisors (8199).
20121 is a wasteful number, since it uses less digits than its factorization.
20121 is an evil number, because the sum of its binary digits is even.
The sum of its prime factors is 375.
The product of its (nonzero) digits is 4, while the sum is 6.
The square root of 20121 is about 141.8485107430.
The cubic root of 20121 is about 27.1988068969.
The spelling of 20121 in words is "twenty thousand, one hundred twenty-one", and thus it is an iban number.