221814991 has 2 divisors, whose sum is σ = 221814992. Its totient is φ = 221814990.

The previous prime is 221814947. The next prime is 221815007. The reversal of 221814991 is 199418122.

221814991 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 221814991 - 2¹⁷ = 221683919 is a prime.

It is a Chen prime.

It is a self number, because there is not a number n which added to its sum of digits gives 221814991.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (221814091) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 110907495 + 110907496.

It is an arithmetic number, because the mean of its divisors is an integer number (110907496).

Almost surely, 2^221814991 is an apocalyptic number.

221814991 is a deficient number, since it is larger than the sum of its proper divisors (1).

221814991 is an equidigital number, since it uses as much as digits as its factorization.

221814991 is an evil number, because the sum of its binary digits is even.

The product of its digits is 10368, while the sum is 37.

The square root of 221814991 is about 14893.4546361816. The cubic root of 221814991 is about 605.3366439173.

It can be divided in two parts, 22181 and 4991, that added together give a palindrome (27172).

The spelling of 221814991 in words is "two hundred twenty-one million, eight hundred fourteen thousand, nine hundred ninety-one".