20812121 has 6 divisors (see below), whose sum is σ = 22876266. Its totient is φ = 18920000.

The previous prime is 20812091. The next prime is 20812123. The reversal of 20812121 is 12121802.

It is a happy number.

It can be written as a sum of positive squares in only one way, i.e., 17106496 + 3705625 = 4136^2 + 1925^2 .

It is a de Polignac number, because none of the positive numbers 2^k-20812121 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 20812121.

It is not an unprimeable number, because it can be changed into a prime (20812123) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 85880 + ... + 86121.

It is an arithmetic number, because the mean of its divisors is an integer number (3812711).

Almost surely, 2^20812121 is an apocalyptic number.

It is an amenable number.

20812121 is a deficient number, since it is larger than the sum of its proper divisors (2064145).

20812121 is a wasteful number, since it uses less digits than its factorization.

20812121 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 172023 (or 172012 counting only the distinct ones).

The product of its (nonzero) digits is 64, while the sum is 17.

The square root of 20812121 is about 4562.0303593904. The cubic root of 20812121 is about 275.0671835854.

Adding to 20812121 its reverse (12121802), we get a palindrome (32933923).

The spelling of 20812121 in words is "twenty million, eight hundred twelve thousand, one hundred twenty-one".