225991 has 4 divisors (see below), whose sum is σ = 229432. Its totient is φ = 222552.

The previous prime is 225989. The next prime is 226001. The reversal of 225991 is 199522.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 199522 = 2 ⋅99761.

It is a cyclic number.

It is not a de Polignac number, because 225991 - 2¹ = 225989 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (225931) 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, 1620 + ... + 1753.

It is an arithmetic number, because the mean of its divisors is an integer number (57358).

2²²⁵⁹⁹¹ is an apocalyptic number.

225991 is a deficient number, since it is larger than the sum of its proper divisors (3441).

225991 is an equidigital number, since it uses as much as digits as its factorization.

225991 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3440.

The product of its digits is 1620, while the sum is 28.

The square root of 225991 is about 475.3851070448. The cubic root of 225991 is about 60.9111849122.

The spelling of 225991 in words is "two hundred twenty-five thousand, nine hundred ninety-one".