21081017 has 2 divisors, whose sum is σ = 21081018. Its totient is φ = 21081016.

The previous prime is 21080987. The next prime is 21081019. The reversal of 21081017 is 71018012.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 16289296 + 4791721 = 4036^2 + 2189^2 .

It is a cyclic number.

It is not a de Polignac number, because 21081017 - 2¹² = 21076921 is a prime.

Together with 21081019, it forms a pair of twin primes.

It is a Chen prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21081017.

It is not a weakly prime, because it can be changed into another prime (21081019) 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, 10540508 + 10540509.

It is an arithmetic number, because the mean of its divisors is an integer number (10540509).

Almost surely, 2^21081017 is an apocalyptic number.

It is an amenable number.

21081017 is a deficient number, since it is larger than the sum of its proper divisors (1).

21081017 is an equidigital number, since it uses as much as digits as its factorization.

21081017 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 112, while the sum is 20.

The square root of 21081017 is about 4591.4068650034. The cubic root of 21081017 is about 276.2467556248.

Adding to 21081017 its reverse (71018012), we get a palindrome (92099029).

It can be divided in two parts, 2108 and 1017, that added together give a 5-th power (3125 = 5⁵).

The spelling of 21081017 in words is "twenty-one million, eighty-one thousand, seventeen".