21366281 has 2 divisors, whose sum is σ = 21366282. Its totient is φ = 21366280.

The previous prime is 21366277. The next prime is 21366311. The reversal of 21366281 is 18266312.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 16679056 + 4687225 = 4084^2 + 2165^2 .

It is a cyclic number.

It is not a de Polignac number, because 21366281 - 2² = 21366277 is a prime.

It is a super-2 number, since 2×21366281² = 913035927541922, which contains 22 as substring.

It is a Sophie Germain prime.

It is a Chen prime.

It is a Curzon number.

It is not a weakly prime, because it can be changed into another prime (21366221) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10683140 + 10683141.

It is an arithmetic number, because the mean of its divisors is an integer number (10683141).

Almost surely, 2^21366281 is an apocalyptic number.

It is an amenable number.

21366281 is a deficient number, since it is larger than the sum of its proper divisors (1).

21366281 is an equidigital number, since it uses as much as digits as its factorization.

21366281 is an evil number, because the sum of its binary digits is even.

The product of its digits is 3456, while the sum is 29.

The square root of 21366281 is about 4622.3674670022. The cubic root of 21366281 is about 277.4872152755.

The spelling of 21366281 in words is "twenty-one million, three hundred sixty-six thousand, two hundred eighty-one".