216891831 has 32 divisors (see below), whose sum is σ = 331224768. Its totient is φ = 125061120.

The previous prime is 216891823. The next prime is 216891907. The reversal of 216891831 is 138198612.

It is not a de Polignac number, because 216891831 - 2³ = 216891823 is a prime.

It is a super-2 number, since 2×216891831² = 94084132709065122, which contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (39).

It is a self number, because there is not a number n which added to its sum of digits gives 216891831.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (216891811) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 183061 + ... + 184241.

It is an arithmetic number, because the mean of its divisors is an integer number (10350774).

Almost surely, 2^216891831 is an apocalyptic number.

216891831 is a deficient number, since it is larger than the sum of its proper divisors (114332937).

216891831 is a wasteful number, since it uses less digits than its factorization.

216891831 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1491.

The product of its digits is 20736, while the sum is 39.

The square root of 216891831 is about 14727.2479099117. The cubic root of 216891831 is about 600.8246355522.

The spelling of 216891831 in words is "two hundred sixteen million, eight hundred ninety-one thousand, eight hundred thirty-one".