20997217 has 2 divisors, whose sum is σ = 20997218. Its totient is φ = 20997216.

The previous prime is 20997211. The next prime is 20997253. The reversal of 20997217 is 71279902.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 20647936 + 349281 = 4544^2 + 591^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-20997217 is a prime.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (20997211) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10498608 + 10498609.

It is an arithmetic number, because the mean of its divisors is an integer number (10498609).

Almost surely, 2^20997217 is an apocalyptic number.

It is an amenable number.

20997217 is a deficient number, since it is larger than the sum of its proper divisors (1).

20997217 is an equidigital number, since it uses as much as digits as its factorization.

20997217 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 15876, while the sum is 37.

The square root of 20997217 is about 4582.2720347007. The cubic root of 20997217 is about 275.8802296616.

It can be divided in two parts, 2099 and 7217, that added together give a triangular number (9316 = T₁₃₆).

The spelling of 20997217 in words is "twenty million, nine hundred ninety-seven thousand, two hundred seventeen".