217120661 has 2 divisors, whose sum is σ = 217120662. Its totient is φ = 217120660.

The previous prime is 217120643. The next prime is 217120693. The reversal of 217120661 is 166021712.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 205348900 + 11771761 = 14330^2 + 3431^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-217120661 is a prime.

It is a Chen prime.

It is a self number, because there is not a number n which added to its sum of digits gives 217120661.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (217170661) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 108560330 + 108560331.

It is an arithmetic number, because the mean of its divisors is an integer number (108560331).

Almost surely, 2^217120661 is an apocalyptic number.

It is an amenable number.

217120661 is a deficient number, since it is larger than the sum of its proper divisors (1).

217120661 is an equidigital number, since it uses as much as digits as its factorization.

217120661 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 1008, while the sum is 26.

The square root of 217120661 is about 14735.0147946991. The cubic root of 217120661 is about 601.0358597027.

The spelling of 217120661 in words is "two hundred seventeen million, one hundred twenty thousand, six hundred sixty-one".