216408591 has 20 divisors (see below), whose sum is σ = 369460432. Its totient is φ = 123661728.

The previous prime is 216408581. The next prime is 216408607. The reversal of 216408591 is 195804612.

216408591 is a `hidden beast` number, since 2 + 1 + 64 + 0 + 8 + 591 = 666.

It is not a de Polignac number, because 216408591 - 2²⁶ = 149299727 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 (216408581) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 19 ways as a sum of consecutive naturals, for example, 190270 + ... + 191403.

Almost surely, 2^216408591 is an apocalyptic number.

216408591 is a gapful number since it is divisible by the number (21) formed by its first and last digit.

216408591 is a deficient number, since it is larger than the sum of its proper divisors (153051841).

216408591 is an equidigital number, since it uses as much as digits as its factorization.

216408591 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 381692 (or 381683 counting only the distinct ones).

The product of its (nonzero) digits is 17280, while the sum is 36.

The square root of 216408591 is about 14710.8324373572. The cubic root of 216408591 is about 600.3780867007.

The spelling of 216408591 in words is "two hundred sixteen million, four hundred eight thousand, five hundred ninety-one".