21108831 has 8 divisors (see below), whose sum is σ = 28403760. Its totient is φ = 13943232.

The previous prime is 21108821. The next prime is 21108847. The reversal of 21108831 is 13880112.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 21108831 - 2¹⁸ = 20846687 is a prime.

It is a super-2 number, since 2×21108831² = 891165492373122, which contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21108811) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 31950 + ... + 32603.

It is an arithmetic number, because the mean of its divisors is an integer number (3550470).

Almost surely, 2^21108831 is an apocalyptic number.

21108831 is a deficient number, since it is larger than the sum of its proper divisors (7294929).

21108831 is a wasteful number, since it uses less digits than its factorization.

21108831 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 64665.

The product of its (nonzero) digits is 384, while the sum is 24.

The square root of 21108831 is about 4594.4347856945. The cubic root of 21108831 is about 276.3681942720.

Adding to 21108831 its reverse (13880112), we get a palindrome (34988943).

The spelling of 21108831 in words is "twenty-one million, one hundred eight thousand, eight hundred thirty-one".