218636989 has 2 divisors, whose sum is σ = 218636990. Its totient is φ = 218636988.

The previous prime is 218636963. The next prime is 218637019. The reversal of 218636989 is 989636812.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 171164889 + 47472100 = 13083^2 + 6890^2 .

It is a cyclic number.

It is not a de Polignac number, because 218636989 - 2⁷ = 218636861 is a prime.

It is a super-2 number, since 2×218636989² = 95604265917972242, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (218636909) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 109318494 + 109318495.

It is an arithmetic number, because the mean of its divisors is an integer number (109318495).

Almost surely, 2^218636989 is an apocalyptic number.

It is an amenable number.

218636989 is a deficient number, since it is larger than the sum of its proper divisors (1).

218636989 is an equidigital number, since it uses as much as digits as its factorization.

218636989 is an evil number, because the sum of its binary digits is even.

The product of its digits is 1119744, while the sum is 52.

The square root of 218636989 is about 14786.3784950880. The cubic root of 218636989 is about 602.4317871846.

The spelling of 218636989 in words is "two hundred eighteen million, six hundred thirty-six thousand, nine hundred eighty-nine".