20812021 has 2 divisors, whose sum is σ = 20812022. Its totient is φ = 20812020.

The previous prime is 20812013. The next prime is 20812039. The reversal of 20812021 is 12021802.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 19236996 + 1575025 = 4386^2 + 1255^2 .

It is a cyclic number.

It is not a de Polignac number, because 20812021 - 2³ = 20812013 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 20811986 and 20812004.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (20812091) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10406010 + 10406011.

It is an arithmetic number, because the mean of its divisors is an integer number (10406011).

Almost surely, 2^20812021 is an apocalyptic number.

It is an amenable number.

20812021 is a deficient number, since it is larger than the sum of its proper divisors (1).

20812021 is an equidigital number, since it uses as much as digits as its factorization.

20812021 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 64, while the sum is 16.

The square root of 20812021 is about 4562.0193993450. The cubic root of 20812021 is about 275.0667430287.

Adding to 20812021 its reverse (12021802), we get a palindrome (32833823).

The spelling of 20812021 in words is "twenty million, eight hundred twelve thousand, twenty-one".