21685111344 has 400 divisors, whose sum is σ = 71324934912. Its totient is φ = 6310503936.

The previous prime is 21685111319. The next prime is 21685111361. The reversal of 21685111344 is 44311158612.

21685111344 is a `hidden beast` number, since 2 + 1 + 6 + 8 + 511 + 134 + 4 = 666.

It is a Harshad number since it is a multiple of its sum of digits (36).

It is a junction number, because it is equal to n+sod(n) for n = 21685111299 and 21685111308.

It is an unprimeable number.

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 79 ways as a sum of consecutive naturals, for example, 41462667 + ... + 41463189.

Almost surely, 2^21685111344 is an apocalyptic number.

21685111344 is a gapful number since it is divisible by the number (24) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21685111344, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (35662467456).

21685111344 is an abundant number, since it is smaller than the sum of its proper divisors (49639823568).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21685111344 is a wasteful number, since it uses less digits than its factorization.

21685111344 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 686 (or 671 counting only the distinct ones).

The product of its digits is 23040, while the sum is 36.

Adding to 21685111344 its reverse (44311158612), we get a palindrome (65996269956).

The spelling of 21685111344 in words is "twenty-one billion, six hundred eighty-five million, one hundred eleven thousand, three hundred forty-four".