221389891 has 4 divisors (see below), whose sum is σ = 221439672. Its totient is φ = 221340112.

The previous prime is 221389877. The next prime is 221389897. The reversal of 221389891 is 198983122.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 221389891 - 2⁵ = 221389859 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (221389897) 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 in 3 ways as a sum of consecutive naturals, for example, 17485 + ... + 27358.

It is an arithmetic number, because the mean of its divisors is an integer number (55359918).

Almost surely, 2^221389891 is an apocalyptic number.

221389891 is a deficient number, since it is larger than the sum of its proper divisors (49781).

221389891 is an equidigital number, since it uses as much as digits as its factorization.

221389891 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 49780.

The product of its digits is 62208, while the sum is 43.

The square root of 221389891 is about 14879.1764221008. The cubic root of 221389891 is about 604.9496950637.

The spelling of 221389891 in words is "two hundred twenty-one million, three hundred eighty-nine thousand, eight hundred ninety-one".