20212121 has 4 divisors (see below), whose sum is σ = 20366544.
Its totient is φ = 20057700.
The previous prime is 20212117. The next prime is 20212151. The reversal of 20212121 is 12121202.
Adding to 20212121 its reverse (12121202), we get a palindrome (32333323).
It can be divided in two parts, 202 and 12121, that multiplied together give a palindrome (2448442).
It is a happy number.
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 20212121 - 22 = 20212117 is a prime.
It is a Duffinian number.
It is a Curzon number.
It is a plaindrome in base 16.
It is not an unprimeable number, because it can be changed into a prime (20212111) 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, 77015 + ... + 77276.
It is an arithmetic number, because the mean of its divisors is an integer number (5091636).
Almost surely, 220212121 is an apocalyptic number.
It is an amenable number.
20212121 is a deficient number, since it is larger than the sum of its proper divisors (154423).
20212121 is a wasteful number, since it uses less digits than its factorization.
20212121 is an evil number, because the sum of its binary digits is even.
The sum of its prime factors is 154422.
The product of its (nonzero) digits is 16, while the sum is 11.
The square root of 20212121 is about 4495.7892521781.
The cubic root of 20212121 is about 272.3980304727.
The spelling of 20212121 in words is "twenty million, two hundred twelve thousand, one hundred twenty-one".