217092990781 has 2 divisors, whose sum is σ = 217092990782. Its totient is φ = 217092990780.

The previous prime is 217092990721. The next prime is 217092990797. The reversal of 217092990781 is 187099290712.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 125641182681 + 91451808100 = 354459^2 + 302410^2 .

It is a cyclic number.

It is not a de Polignac number, because 217092990781 - 2²⁹ = 216556119869 is a prime.

It is a super-2 number, since 2×217092990781² (a number of 23 digits) contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (217092990721) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 108546495390 + 108546495391.

It is an arithmetic number, because the mean of its divisors is an integer number (108546495391).

Almost surely, 2^217092990781 is an apocalyptic number.

It is an amenable number.

217092990781 is a deficient number, since it is larger than the sum of its proper divisors (1).

217092990781 is an equidigital number, since it uses as much as digits as its factorization.

217092990781 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 1143072, while the sum is 55.

The spelling of 217092990781 in words is "two hundred seventeen billion, ninety-two million, nine hundred ninety thousand, seven hundred eighty-one".