21609017 has 2 divisors, whose sum is σ = 21609018. Its totient is φ = 21609016.

The previous prime is 21609013. The next prime is 21609019. The reversal of 21609017 is 71090612.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 18567481 + 3041536 = 4309^2 + 1744^2 .

It is a cyclic number.

It is not a de Polignac number, because 21609017 - 2² = 21609013 is a prime.

Together with 21609019, it forms a pair of twin primes.

It is a Chen prime.

It is a zygodrome in base 3.

It is not a weakly prime, because it can be changed into another prime (21609011) 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, 10804508 + 10804509.

It is an arithmetic number, because the mean of its divisors is an integer number (10804509).

Almost surely, 2^21609017 is an apocalyptic number.

It is an amenable number.

21609017 is a deficient number, since it is larger than the sum of its proper divisors (1).

21609017 is an equidigital number, since it uses as much as digits as its factorization.

21609017 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 756, while the sum is 26.

The square root of 21609017 is about 4648.5499889751. The cubic root of 21609017 is about 278.5340775945.

Adding to 21609017 its reverse (71090612), we get a palindrome (92699629).

The spelling of 21609017 in words is "twenty-one million, six hundred nine thousand, seventeen".