20928217 has 2 divisors, whose sum is σ = 20928218. Its totient is φ = 20928216.

The previous prime is 20928209. The next prime is 20928223. The reversal of 20928217 is 71282902.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 19545241 + 1382976 = 4421^2 + 1176^2 .

It is a cyclic number.

It is not a de Polignac number, because 20928217 - 2³ = 20928209 is a prime.

It is not a weakly prime, because it can be changed into another prime (20928247) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10464108 + 10464109.

It is an arithmetic number, because the mean of its divisors is an integer number (10464109).

Almost surely, 2^20928217 is an apocalyptic number.

It is an amenable number.

20928217 is a deficient number, since it is larger than the sum of its proper divisors (1).

20928217 is an equidigital number, since it uses as much as digits as its factorization.

20928217 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 4032, while the sum is 31.

The square root of 20928217 is about 4574.7368230315. The cubic root of 20928217 is about 275.5777034519.

The spelling of 20928217 in words is "twenty million, nine hundred twenty-eight thousand, two hundred seventeen".