218955661 has 2 divisors, whose sum is σ = 218955662. Its totient is φ = 218955660.

The previous prime is 218955643. The next prime is 218955673. The reversal of 218955661 is 166559812.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 143161225 + 75794436 = 11965^2 + 8706^2 .

It is a cyclic number.

It is not a de Polignac number, because 218955661 - 2⁵ = 218955629 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (218955641) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 109477830 + 109477831.

It is an arithmetic number, because the mean of its divisors is an integer number (109477831).

Almost surely, 2^218955661 is an apocalyptic number.

It is an amenable number.

218955661 is a deficient number, since it is larger than the sum of its proper divisors (1).

218955661 is an equidigital number, since it uses as much as digits as its factorization.

218955661 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 129600, while the sum is 43.

The square root of 218955661 is about 14797.1504351345. The cubic root of 218955661 is about 602.7243344291.

It can be divided in two parts, 21895 and 5661, that added together give a square (27556 = 166²).

The spelling of 218955661 in words is "two hundred eighteen million, nine hundred fifty-five thousand, six hundred sixty-one".