21681550381344 has 384 divisors, whose sum is σ = 67366077553152. Its totient is φ = 5977064079360.

The previous prime is 21681550381339. The next prime is 21681550381363. The reversal of 21681550381344 is 44318305518612.

It is an unprimeable number.

It is a polite number, since it can be written in 63 ways as a sum of consecutive naturals, for example, 6352635382 + ... + 6352638794.

It is an arithmetic number, because the mean of its divisors is an integer number (175432493628).

Almost surely, 2^{21681550381344} is an apocalyptic number.

21681550381344 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 21681550381344, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (33683038776576).

21681550381344 is an abundant number, since it is smaller than the sum of its proper divisors (45684527171808).

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

21681550381344 is a wasteful number, since it uses less digits than its factorization.

21681550381344 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5948 (or 5940 counting only the distinct ones).

The product of its (nonzero) digits is 2764800, while the sum is 51.

Adding to 21681550381344 its reverse (44318305518612), we get a palindrome (65999855899956).

The spelling of 21681550381344 in words is "twenty-one trillion, six hundred eighty-one billion, five hundred fifty million, three hundred eighty-one thousand, three hundred forty-four".