21966281 has 2 divisors, whose sum is σ = 21966282. Its totient is φ = 21966280.

The previous prime is 21966257. The next prime is 21966289. The reversal of 21966281 is 18266912.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 20620681 + 1345600 = 4541^2 + 1160^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21966281 is a prime.

It is a super-2 number, since 2×21966281² = 965035001941922, which contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (21966289) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10983140 + 10983141.

It is an arithmetic number, because the mean of its divisors is an integer number (10983141).

Almost surely, 2^21966281 is an apocalyptic number.

It is an amenable number.

21966281 is a deficient number, since it is larger than the sum of its proper divisors (1).

21966281 is an equidigital number, since it uses as much as digits as its factorization.

21966281 is an evil number, because the sum of its binary digits is even.

The product of its digits is 10368, while the sum is 35.

The square root of 21966281 is about 4686.8199239996. The cubic root of 21966281 is about 280.0607053752.

The spelling of 21966281 in words is "twenty-one million, nine hundred sixty-six thousand, two hundred eighty-one".