21127817 has 2 divisors, whose sum is σ = 21127818. Its totient is φ = 21127816.

The previous prime is 21127783. The next prime is 21127819. The reversal of 21127817 is 71872112.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 14258176 + 6869641 = 3776^2 + 2621^2 .

It is a cyclic number.

It is not a de Polignac number, because 21127817 - 2¹² = 21123721 is a prime.

Together with 21127819, 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 21127817.

It is not a weakly prime, because it can be changed into another prime (21127819) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10563908 + 10563909.

It is an arithmetic number, because the mean of its divisors is an integer number (10563909).

Almost surely, 2^21127817 is an apocalyptic number.

It is an amenable number.

21127817 is a deficient number, since it is larger than the sum of its proper divisors (1).

21127817 is an equidigital number, since it uses as much as digits as its factorization.

21127817 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 1568, while the sum is 29.

The square root of 21127817 is about 4596.5005166975. The cubic root of 21127817 is about 276.4510277580.

Adding to 21127817 its reverse (71872112), we get a palindrome (92999929).

The spelling of 21127817 in words is "twenty-one million, one hundred twenty-seven thousand, eight hundred seventeen".