221678081 has 2 divisors, whose sum is σ = 221678082. Its totient is φ = 221678080.

The previous prime is 221678047. The next prime is 221678099. The reversal of 221678081 is 180876122.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 219306481 + 2371600 = 14809^2 + 1540^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-221678081 is a prime.

It is a super-2 number, since 2×221678081² = 98282343191685122, which contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (221672081) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 110839040 + 110839041.

It is an arithmetic number, because the mean of its divisors is an integer number (110839041).

Almost surely, 2^221678081 is an apocalyptic number.

It is an amenable number.

221678081 is a deficient number, since it is larger than the sum of its proper divisors (1).

221678081 is an equidigital number, since it uses as much as digits as its factorization.

221678081 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 10752, while the sum is 35.

The square root of 221678081 is about 14888.8576123220. The cubic root of 221678081 is about 605.2120750944.

The spelling of 221678081 in words is "two hundred twenty-one million, six hundred seventy-eight thousand, eighty-one".