21044121840 has 1280 divisors, whose sum is σ = 95993856000. Its totient is φ = 4120657920.

The previous prime is 21044121811. The next prime is 21044121863. The reversal of 21044121840 is 4812144012.

21044121840 is a `hidden beast` number, since 2 + 1 + 0 + 441 + 218 + 4 + 0 = 666.

It is a Harshad number since it is a multiple of its sum of digits (27).

It is a congruent number.

It is an unprimeable number.

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 255 ways as a sum of consecutive naturals, for example, 151396491 + ... + 151396629.

It is an arithmetic number, because the mean of its divisors is an integer number (74995200).

Almost surely, 2^21044121840 is an apocalyptic number.

21044121840 is a gapful number since it is divisible by the number (20) 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 21044121840, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (47996928000).

21044121840 is an abundant number, since it is smaller than the sum of its proper divisors (74949734160).

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

21044121840 is a wasteful number, since it uses less digits than its factorization.

21044121840 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 235 (or 223 counting only the distinct ones).

The product of its (nonzero) digits is 2048, while the sum is 27.

Adding to 21044121840 its reverse (4812144012), we get a palindrome (25856265852).

It can be divided in two parts, 21044 and 121840, that added together give a square (142884 = 378²).

The spelling of 21044121840 in words is "twenty-one billion, forty-four million, one hundred twenty-one thousand, eight hundred forty".