217457649781 has 2 divisors, whose sum is σ = 217457649782. Its totient is φ = 217457649780.

The previous prime is 217457649757. The next prime is 217457649817. The reversal of 217457649781 is 187946754712.

It is a happy number.

217457649781 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

Together with next prime (217457649817) it forms an Ormiston pair, because they use the same digits, order apart.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 167162411025 + 50295238756 = 408855^2 + 224266^2 .

It is a cyclic number.

It is not a de Polignac number, because 217457649781 - 2²⁹ = 216920778869 is a prime.

It is a super-3 number, since 3×217457649781³ (a number of 35 digits) contains 333 as substring. Note that it is a super-d number also for d = 2.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (217457649881) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 108728824890 + 108728824891.

It is an arithmetic number, because the mean of its divisors is an integer number (108728824891).

Almost surely, 2^217457649781 is an apocalyptic number.

It is an amenable number.

217457649781 is a deficient number, since it is larger than the sum of its proper divisors (1).

217457649781 is an equidigital number, since it uses as much as digits as its factorization.

217457649781 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 23708160, while the sum is 61.

The spelling of 217457649781 in words is "two hundred seventeen billion, four hundred fifty-seven million, six hundred forty-nine thousand, seven hundred eighty-one".