21161717 has 2 divisors, whose sum is σ = 21161718. Its totient is φ = 21161716.

The previous prime is 21161683. The next prime is 21161729. The reversal of 21161717 is 71716112.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 21031396 + 130321 = 4586^2 + 361^2 .

It is a cyclic number.

It is not a de Polignac number, because 21161717 - 2⁶ = 21161653 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21161737) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10580858 + 10580859.

It is an arithmetic number, because the mean of its divisors is an integer number (10580859).

Almost surely, 2^21161717 is an apocalyptic number.

It is an amenable number.

21161717 is a deficient number, since it is larger than the sum of its proper divisors (1).

21161717 is an equidigital number, since it uses as much as digits as its factorization.

21161717 is an evil number, because the sum of its binary digits is even.

The product of its digits is 588, while the sum is 26.

The square root of 21161717 is about 4600.1866266490. The cubic root of 21161717 is about 276.5988057948.

Adding to 21161717 its reverse (71716112), we get a palindrome (92877829).

The spelling of 21161717 in words is "twenty-one million, one hundred sixty-one thousand, seven hundred seventeen".