21216404331 has 8 divisors (see below), whose sum is σ = 31431710160. Its totient is φ = 14144269536.

The previous prime is 21216404323. The next prime is 21216404351. The reversal of 21216404331 is 13340461212.

It is a happy number.

21216404331 is a `hidden beast` number, since 2 + 12 + 1 + 640 + 4 + 3 + 3 + 1 = 666.

It is not a de Polignac number, because 21216404331 - 2³ = 21216404323 is a prime.

It is a super-3 number, since 3×21216404331³ (a number of 32 digits) contains 333 as substring. Note that it is a super-d number also for d = 2.

It is a Harshad number since it is a multiple of its sum of digits (27), and also a Moran number because the ratio is a prime number: 785792753 = 21216404331 / (2 + 1 + 2 + 1 + 6 + 4 + 0 + 4 + 3 + 3 + 1).

It is a junction number, because it is equal to n+sod(n) for n = 21216404295 and 21216404304.

It is not an unprimeable number, because it can be changed into a prime (21216404351) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 392896350 + ... + 392896403.

It is an arithmetic number, because the mean of its divisors is an integer number (3928963770).

Almost surely, 2^21216404331 is an apocalyptic number.

21216404331 is a deficient number, since it is larger than the sum of its proper divisors (10215305829).

21216404331 is an equidigital number, since it uses as much as digits as its factorization.

21216404331 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 785792762 (or 785792756 counting only the distinct ones).

The product of its (nonzero) digits is 3456, while the sum is 27.

Adding to 21216404331 its reverse (13340461212), we get a palindrome (34556865543).

The spelling of 21216404331 in words is "twenty-one billion, two hundred sixteen million, four hundred four thousand, three hundred thirty-one".