215591 has 4 divisors (see below), whose sum is σ = 218400. Its totient is φ = 212784.

The previous prime is 215587. The next prime is 215617. The reversal of 215591 is 195512.

215591 = 8² + 9² + ... + 86².

215591 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

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 215591 - 2² = 215587 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 (215521) 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, 1286 + ... + 1443.

It is an arithmetic number, because the mean of its divisors is an integer number (54600).

2²¹⁵⁵⁹¹ is an apocalyptic number.

215591 is a deficient number, since it is larger than the sum of its proper divisors (2809).

215591 is an equidigital number, since it uses as much as digits as its factorization.

215591 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2808.

The product of its digits is 450, while the sum is 23.

The square root of 215591 is about 464.3177791125. The cubic root of 215591 is about 59.9621057017.

The spelling of 215591 in words is "two hundred fifteen thousand, five hundred ninety-one".