216556881 has 4 divisors (see below), whose sum is σ = 288742512. Its totient is φ = 144371252.

The previous prime is 216556867. The next prime is 216556903. The reversal of 216556881 is 188655612.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 216556881 - 2⁶ = 216556817 is a prime.

It is a super-2 number, since 2×216556881² = 93793765416896322, which contains 22 as substring.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (216556811) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 36092811 + ... + 36092816.

It is an arithmetic number, because the mean of its divisors is an integer number (72185628).

Almost surely, 2^216556881 is an apocalyptic number.

It is an amenable number.

216556881 is a deficient number, since it is larger than the sum of its proper divisors (72185631).

216556881 is an equidigital number, since it uses as much as digits as its factorization.

216556881 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 72185630.

The product of its digits is 115200, while the sum is 42.

The square root of 216556881 is about 14715.8717376851. The cubic root of 216556881 is about 600.5151880644.

The spelling of 216556881 in words is "two hundred sixteen million, five hundred fifty-six thousand, eight hundred eighty-one".