221391 has 12 divisors (see below), whose sum is σ = 338832. Its totient is φ = 138816.

The previous prime is 221327. The next prime is 221393. The reversal of 221391 is 193122.

It is a happy number.

It is not a de Polignac number, because 221391 - 2⁶ = 221327 is a prime.

221391 is a lucky number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (221393) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 571 + ... + 876.

It is an arithmetic number, because the mean of its divisors is an integer number (28236).

2²²¹³⁹¹ is an apocalyptic number.

221391 is a deficient number, since it is larger than the sum of its proper divisors (117441).

221391 is a wasteful number, since it uses less digits than its factorization.

221391 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1470 (or 1467 counting only the distinct ones).

The product of its digits is 108, while the sum is 18.

The square root of 221391 is about 470.5220504929. The cubic root of 221391 is about 60.4950705179.

It can be divided in two parts, 2213 and 91, that added together give a square (2304 = 48²).

The spelling of 221391 in words is "two hundred twenty-one thousand, three hundred ninety-one".