20970221 has 2 divisors, whose sum is σ = 20970222. Its totient is φ = 20970220.

The previous prime is 20970203. The next prime is 20970223. The reversal of 20970221 is 12207902.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 17547721 + 3422500 = 4189^2 + 1850^2 .

It is a cyclic number.

It is not a de Polignac number, because 20970221 - 2¹⁰ = 20969197 is a prime.

It is a Sophie Germain prime.

Together with 20970223, it forms a pair of twin primes.

It is a Chen prime.

It is a Curzon number.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (20970223) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10485110 + 10485111.

It is an arithmetic number, because the mean of its divisors is an integer number (10485111).

Almost surely, 2^20970221 is an apocalyptic number.

It is an amenable number.

20970221 is a deficient number, since it is larger than the sum of its proper divisors (1).

20970221 is an equidigital number, since it uses as much as digits as its factorization.

20970221 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 504, while the sum is 23.

The square root of 20970221 is about 4579.3253869975. The cubic root of 20970221 is about 275.7619464185.

The spelling of 20970221 in words is "twenty million, nine hundred seventy thousand, two hundred twenty-one".