21066257 has 2 divisors, whose sum is σ = 21066258. Its totient is φ = 21066256.

The previous prime is 21066239. The next prime is 21066263. The reversal of 21066257 is 75266012.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 16777216 + 4289041 = 4096^2 + 2071^2 .

It is a cyclic number.

It is not a de Polignac number, because 21066257 - 2²⁰ = 20017681 is a prime.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (21066217) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10533128 + 10533129.

It is an arithmetic number, because the mean of its divisors is an integer number (10533129).

Almost surely, 2^21066257 is an apocalyptic number.

It is an amenable number.

21066257 is a deficient number, since it is larger than the sum of its proper divisors (1).

21066257 is an equidigital number, since it uses as much as digits as its factorization.

21066257 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 5040, while the sum is 29.

The square root of 21066257 is about 4589.7992330820. The cubic root of 21066257 is about 276.1822686334.

The spelling of 21066257 in words is "twenty-one million, sixty-six thousand, two hundred fifty-seven".