218639881 has 2 divisors, whose sum is σ = 218639882. Its totient is φ = 218639880.

The previous prime is 218639849. The next prime is 218639929. The reversal of 218639881 is 188936812.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 168584256 + 50055625 = 12984^2 + 7075^2 .

It is a cyclic number.

It is not a de Polignac number, because 218639881 - 2⁵ = 218639849 is a prime.

It is a super-2 number, since 2×218639881² = 95606795127388322, which contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (218639581) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 109319940 + 109319941.

It is an arithmetic number, because the mean of its divisors is an integer number (109319941).

Almost surely, 2^218639881 is an apocalyptic number.

It is an amenable number.

218639881 is a deficient number, since it is larger than the sum of its proper divisors (1).

218639881 is an equidigital number, since it uses as much as digits as its factorization.

218639881 is an evil number, because the sum of its binary digits is even.

The product of its digits is 165888, while the sum is 46.

The square root of 218639881 is about 14786.4762874730. The cubic root of 218639881 is about 602.4344433760.

The spelling of 218639881 in words is "two hundred eighteen million, six hundred thirty-nine thousand, eight hundred eighty-one".