221605591 has 4 divisors (see below), whose sum is σ = 234641232. Its totient is φ = 208569952.

The previous prime is 221605567. The next prime is 221605597. The reversal of 221605591 is 195506122.

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 221605591 - 2⁷ = 221605463 is a prime.

It is a super-3 number, since 3×221605591³ (a number of 26 digits) contains 333 as substring.

It is a Smith number, since the sum of its digits (31) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (221605597) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 6517795 + ... + 6517828.

It is an arithmetic number, because the mean of its divisors is an integer number (58660308).

Almost surely, 2^221605591 is an apocalyptic number.

221605591 is a deficient number, since it is larger than the sum of its proper divisors (13035641).

221605591 is a wasteful number, since it uses less digits than its factorization.

221605591 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 13035640.

The product of its (nonzero) digits is 5400, while the sum is 31.

The square root of 221605591 is about 14886.4230424908. The cubic root of 221605591 is about 605.1460986327.

The spelling of 221605591 in words is "two hundred twenty-one million, six hundred five thousand, five hundred ninety-one".