21281017 has 2 divisors, whose sum is σ = 21281018. Its totient is φ = 21281016.

The previous prime is 21281011. The next prime is 21281021. The reversal of 21281017 is 71018212.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 12257001 + 9024016 = 3501^2 + 3004^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21281017 is a prime.

It is a Chen prime.

It is equal to p_1346611 and since 21281017 and 1346611 have the same sum of digits, it is a Honaker prime.

It is not a weakly prime, because it can be changed into another prime (21281011) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10640508 + 10640509.

It is an arithmetic number, because the mean of its divisors is an integer number (10640509).

Almost surely, 2^21281017 is an apocalyptic number.

It is an amenable number.

21281017 is a deficient number, since it is larger than the sum of its proper divisors (1).

21281017 is an equidigital number, since it uses as much as digits as its factorization.

21281017 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 224, while the sum is 22.

The square root of 21281017 is about 4613.1352679062. The cubic root of 21281017 is about 277.1176109151.

Adding to 21281017 its reverse (71018212), we get a palindrome (92299229).

The spelling of 21281017 in words is "twenty-one million, two hundred eighty-one thousand, seventeen".