21017 has 2 divisors, whose sum is σ = 21018. Its totient is φ = 21016.

The previous prime is 21013. The next prime is 21019. The reversal of 21017 is 71012.

Adding to 21017 its reverse (71012), we get a palindrome (92029).

It can be divided in two parts, 210 and 17, that multiplied together give a triangular number (3570 = T_{84}).

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 10816 + 10201 = 104^2 + 101^2 .

It is a cyclic number.

It is not a de Polignac number, because 21017 - 2^{2} = 21013 is a prime.

Together with 21019, it forms a pair of twin primes.

It is a Chen prime.

It is an Ulam number.

It is a junction number, because it is equal to *n*+sod(*n*) for *n* = 20989 and 21007.

It is an inconsummate number, since it does not exist a number *n* which divided by its sum of digits gives 21017.

It is not a weakly prime, because it can be changed into another prime (21011) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10508 + 10509.

It is an arithmetic number, because the mean of its divisors is an integer number (10509).

2^{21017} is an apocalyptic number.

It is an amenable number.

21017 is a deficient number, since it is larger than the sum of its proper divisors (1).

21017 is an equidigital number, since it uses as much as digits as its factorization.

21017 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 14, while the sum is 11.

The square root of 21017 is about 144.9724111685. The cubic root of 21017 is about 27.5966844719.

The spelling of 21017 in words is "twenty-one thousand, seventeen", and thus it is an iban number.

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