216706661 has 2 divisors, whose sum is σ = 216706662. Its totient is φ = 216706660.

The previous prime is 216706657. The next prime is 216706681. The reversal of 216706661 is 166607612.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 210076036 + 6630625 = 14494^2 + 2575^2 .

It is a cyclic number.

It is not a de Polignac number, because 216706661 - 2² = 216706657 is a prime.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (216706601) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 108353330 + 108353331.

It is an arithmetic number, because the mean of its divisors is an integer number (108353331).

Almost surely, 2^216706661 is an apocalyptic number.

It is an amenable number.

216706661 is a deficient number, since it is larger than the sum of its proper divisors (1).

216706661 is an equidigital number, since it uses as much as digits as its factorization.

216706661 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 18144, while the sum is 35.

The square root of 216706661 is about 14720.9599211464. The cubic root of 216706661 is about 600.6536034863.

The spelling of 216706661 in words is "two hundred sixteen million, seven hundred six thousand, six hundred sixty-one".