216387191 has 4 divisors (see below), whose sum is σ = 219934584. Its totient is φ = 212839800.

The previous prime is 216387179. The next prime is 216387221. The reversal of 216387191 is 191783612.

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 216387191 - 2¹⁸ = 216125047 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 (216387121) 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, 1773605 + ... + 1773726.

It is an arithmetic number, because the mean of its divisors is an integer number (54983646).

Almost surely, 2^216387191 is an apocalyptic number.

216387191 is a deficient number, since it is larger than the sum of its proper divisors (3547393).

216387191 is an equidigital number, since it uses as much as digits as its factorization.

216387191 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3547392.

The product of its digits is 18144, while the sum is 38.

The square root of 216387191 is about 14710.1050642067. The cubic root of 216387191 is about 600.3582961823.

The spelling of 216387191 in words is "two hundred sixteen million, three hundred eighty-seven thousand, one hundred ninety-one".