20972221 has 2 divisors, whose sum is σ = 20972222. Its totient is φ = 20972220.

The previous prime is 20972179. The next prime is 20972233. The reversal of 20972221 is 12227902.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 16088121 + 4884100 = 4011^2 + 2210^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-20972221 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (20972291) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10486110 + 10486111.

It is an arithmetic number, because the mean of its divisors is an integer number (10486111).

Almost surely, 2^20972221 is an apocalyptic number.

It is an amenable number.

20972221 is a deficient number, since it is larger than the sum of its proper divisors (1).

20972221 is an equidigital number, since it uses as much as digits as its factorization.

20972221 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 1008, while the sum is 25.

The square root of 20972221 is about 4579.5437545677. The cubic root of 20972221 is about 275.7707129191.

The spelling of 20972221 in words is "twenty million, nine hundred seventy-two thousand, two hundred twenty-one".