217561165649 has 4 divisors (see below), whose sum is σ = 217585540260. Its totient is φ = 217536791040.

The previous prime is 217561165579. The next prime is 217561165651. The reversal of 217561165649 is 946561165712.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 50122254400 + 167438911249 = 223880^2 + 409193^2 .

It is a cyclic number.

It is not a de Polignac number, because 217561165649 - 2¹² = 217561161553 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 217561165649.

It is not an unprimeable number, because it can be changed into a prime (217561165249) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (23) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 12173912 + ... + 12191769.

It is an arithmetic number, because the mean of its divisors is an integer number (54396385065).

Almost surely, 2^217561165649 is an apocalyptic number.

It is an amenable number.

217561165649 is a deficient number, since it is larger than the sum of its proper divisors (24374611).

217561165649 is an equidigital number, since it uses as much as digits as its factorization.

217561165649 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 24374610.

The product of its digits is 2721600, while the sum is 53.

The spelling of 217561165649 in words is "two hundred seventeen billion, five hundred sixty-one million, one hundred sixty-five thousand, six hundred forty-nine".