21668131249217 has 2 divisors, whose sum is σ = 21668131249218. Its totient is φ = 21668131249216.

The previous prime is 21668131249201. The next prime is 21668131249307. The reversal of 21668131249217 is 71294213186612.

It is a Cunningham number, because it is equal to 4654904²+1.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 21668131249216 + 1 = 4654904^2 + 1^2 .

It is a cyclic number.

It is not a de Polignac number, because 21668131249217 - 2⁴ = 21668131249201 is a prime.

It is a super-2 number, since 2×21668131249217² (a number of 27 digits) contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (21668131249117) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10834065624608 + 10834065624609.

It is an arithmetic number, because the mean of its divisors is an integer number (10834065624609).

Almost surely, 2^{21668131249217} is an apocalyptic number.

It is an amenable number.

21668131249217 is a deficient number, since it is larger than the sum of its proper divisors (1).

21668131249217 is an equidigital number, since it uses as much as digits as its factorization.

21668131249217 is an evil number, because the sum of its binary digits is even.

The product of its digits is 1741824, while the sum is 53.

The spelling of 21668131249217 in words is "twenty-one trillion, six hundred sixty-eight billion, one hundred thirty-one million, two hundred forty-nine thousand, two hundred seventeen".