216666493 has 2 divisors, whose sum is σ = 216666494. Its totient is φ = 216666492.

The previous prime is 216666473. The next prime is 216666497. The reversal of 216666493 is 394666612.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 149377284 + 67289209 = 12222^2 + 8203^2 .

It is a cyclic number.

It is not a de Polignac number, because 216666493 - 2¹³ = 216658301 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (216666497) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 108333246 + 108333247.

It is an arithmetic number, because the mean of its divisors is an integer number (108333247).

Almost surely, 2^216666493 is an apocalyptic number.

It is an amenable number.

216666493 is a deficient number, since it is larger than the sum of its proper divisors (1).

216666493 is an equidigital number, since it uses as much as digits as its factorization.

216666493 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 279936, while the sum is 43.

The square root of 216666493 is about 14719.5955447152. The cubic root of 216666493 is about 600.6164894990.

The spelling of 216666493 in words is "two hundred sixteen million, six hundred sixty-six thousand, four hundred ninety-three".