218195981 has 12 divisors (see below), whose sum is σ = 230940864. Its totient is φ = 206123400.

The previous prime is 218195977. The next prime is 218195987. The reversal of 218195981 is 189591812.

It is not a de Polignac number, because 218195981 - 2² = 218195977 is a prime.

It is a super-2 number, since 2×218195981² = 95218972249104722, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (218195987) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 176636 + ... + 177866.

It is an arithmetic number, because the mean of its divisors is an integer number (19245072).

Almost surely, 2^218195981 is an apocalyptic number.

It is an amenable number.

218195981 is a deficient number, since it is larger than the sum of its proper divisors (12744883).

218195981 is a wasteful number, since it uses less digits than its factorization.

218195981 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1760 (or 1741 counting only the distinct ones).

The product of its digits is 51840, while the sum is 44.

The square root of 218195981 is about 14771.4583234019. The cubic root of 218195981 is about 602.0264637763.

The spelling of 218195981 in words is "two hundred eighteen million, one hundred ninety-five thousand, nine hundred eighty-one".