221428187 has 2 divisors, whose sum is σ = 221428188. Its totient is φ = 221428186.

The previous prime is 221428127. The next prime is 221428189. The reversal of 221428187 is 781824122.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 221428187 - 2⁸ = 221427931 is a prime.

Together with 221428189, it forms a pair of twin primes.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (221428189) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 110714093 + 110714094.

It is an arithmetic number, because the mean of its divisors is an integer number (110714094).

Almost surely, 2^221428187 is an apocalyptic number.

221428187 is a deficient number, since it is larger than the sum of its proper divisors (1).

221428187 is an equidigital number, since it uses as much as digits as its factorization.

221428187 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 14336, while the sum is 35.

The square root of 221428187 is about 14880.4632656379. The cubic root of 221428187 is about 604.9845744308.

The spelling of 221428187 in words is "two hundred twenty-one million, four hundred twenty-eight thousand, one hundred eighty-seven".