20215021 has 2 divisors, whose sum is σ = 20215022. Its totient is φ = 20215020.

The previous prime is 20214991. The next prime is 20215033. The reversal of 20215021 is 12051202.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 13402921 + 6812100 = 3661^2 + 2610^2 .

It is a cyclic number.

It is not a de Polignac number, because 20215021 - 2⁷ = 20214893 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 20214992 and 20215010.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (20215621) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10107510 + 10107511.

It is an arithmetic number, because the mean of its divisors is an integer number (10107511).

Almost surely, 2^20215021 is an apocalyptic number.

It is an amenable number.

20215021 is a deficient number, since it is larger than the sum of its proper divisors (1).

20215021 is an equidigital number, since it uses as much as digits as its factorization.

20215021 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 40, while the sum is 13.

The square root of 20215021 is about 4496.1117646251. Note that the first 3 decimals coincide. The cubic root of 20215021 is about 272.4110575817.

Adding to 20215021 its reverse (12051202), we get a palindrome (32266223).

The spelling of 20215021 in words is "twenty million, two hundred fifteen thousand, twenty-one".