20100121 has 4 divisors (see below), whose sum is σ = 20748544. Its totient is φ = 19451700.

The previous prime is 20100097. The next prime is 20100149. The reversal of 20100121 is 12100102.

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.

It is a cyclic number.

It is not a de Polignac number, because 20100121 - 2²¹ = 18002969 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (20100151) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 324165 + ... + 324226.

It is an arithmetic number, because the mean of its divisors is an integer number (5187136).

Almost surely, 2^20100121 is an apocalyptic number.

It is an amenable number.

20100121 is a deficient number, since it is larger than the sum of its proper divisors (648423).

20100121 is an equidigital number, since it uses as much as digits as its factorization.

20100121 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 648422.

The product of its (nonzero) digits is 4, while the sum is 7.

The square root of 20100121 is about 4483.3158487887. The cubic root of 20100121 is about 271.8939582675.

Adding to 20100121 its reverse (12100102), we get a palindrome (32200223).

The spelling of 20100121 in words is "twenty million, one hundred thousand, one hundred twenty-one".