215891 has 4 divisors (see below), whose sum is σ = 232512. Its totient is φ = 199272.

The previous prime is 215863. The next prime is 215893. The reversal of 215891 is 198512.

It is a happy number.

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 215891 - 2⁶ = 215827 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 215891.

It is not an unprimeable number, because it can be changed into a prime (215893) 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, 8291 + ... + 8316.

It is an arithmetic number, because the mean of its divisors is an integer number (58128).

2²¹⁵⁸⁹¹ is an apocalyptic number.

215891 is a deficient number, since it is larger than the sum of its proper divisors (16621).

215891 is a wasteful number, since it uses less digits than its factorization.

215891 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 16620.

The product of its digits is 720, while the sum is 26.

The square root of 215891 is about 464.6407214182. The cubic root of 215891 is about 59.9899057093.

The spelling of 215891 in words is "two hundred fifteen thousand, eight hundred ninety-one".