217608745691 has 2 divisors, whose sum is σ = 217608745692. Its totient is φ = 217608745690.

The previous prime is 217608745661. The next prime is 217608745741. The reversal of 217608745691 is 196547806712.

It is a happy number.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 217608745691 - 2¹⁴ = 217608729307 is a prime.

It is a super-2 number, since 2×217608745691² (a number of 23 digits) contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (217608745661) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 108804372845 + 108804372846.

It is an arithmetic number, because the mean of its divisors is an integer number (108804372846).

Almost surely, 2^217608745691 is an apocalyptic number.

217608745691 is a deficient number, since it is larger than the sum of its proper divisors (1).

217608745691 is an equidigital number, since it uses as much as digits as its factorization.

217608745691 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 5080320, while the sum is 56.

The spelling of 217608745691 in words is "two hundred seventeen billion, six hundred eight million, seven hundred forty-five thousand, six hundred ninety-one".