21966257 has 2 divisors, whose sum is σ = 21966258. Its totient is φ = 21966256.

The previous prime is 21966239. The next prime is 21966281. The reversal of 21966257 is 75266912.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 19749136 + 2217121 = 4444^2 + 1489^2 .

It is a cyclic number.

It is not a de Polignac number, because 21966257 - 2¹⁰ = 21965233 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21966257.

It is not a weakly prime, because it can be changed into another prime (21966757) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10983128 + 10983129.

It is an arithmetic number, because the mean of its divisors is an integer number (10983129).

Almost surely, 2^21966257 is an apocalyptic number.

It is an amenable number.

21966257 is a deficient number, since it is larger than the sum of its proper divisors (1).

21966257 is an equidigital number, since it uses as much as digits as its factorization.

21966257 is an evil number, because the sum of its binary digits is even.

The product of its digits is 45360, while the sum is 38.

The square root of 21966257 is about 4686.8173636275. The cubic root of 21966257 is about 280.0606033786.

The spelling of 21966257 in words is "twenty-one million, nine hundred sixty-six thousand, two hundred fifty-seven".