21696217 has 2 divisors, whose sum is σ = 21696218. Its totient is φ = 21696216.

The previous prime is 21696211. The next prime is 21696277. The reversal of 21696217 is 71269612.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 18071001 + 3625216 = 4251^2 + 1904^2 .

It is a cyclic number.

It is not a de Polignac number, because 21696217 - 2¹⁹ = 21171929 is a prime.

It is a super-2 number, since 2×21696217² = 941451664222178, which contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (21696211) 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, 10848108 + 10848109.

It is an arithmetic number, because the mean of its divisors is an integer number (10848109).

Almost surely, 2^21696217 is an apocalyptic number.

It is an amenable number.

21696217 is a deficient number, since it is larger than the sum of its proper divisors (1).

21696217 is an equidigital number, since it uses as much as digits as its factorization.

21696217 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 9072, while the sum is 34.

The square root of 21696217 is about 4657.9198146812. The cubic root of 21696217 is about 278.9082358169.

The spelling of 21696217 in words is "twenty-one million, six hundred ninety-six thousand, two hundred seventeen".