21281138424 has 960 divisors, whose sum is σ = 82648304640. Its totient is φ = 4981616640.

The previous prime is 21281138393. The next prime is 21281138477. The reversal of 21281138424 is 42483118212.

21281138424 is a `hidden beast` number, since 21 + 2 + 81 + 138 + 424 = 666.

It is a super-3 number, since 3×21281138424³ (a number of 32 digits) contains 333 as substring.

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

It is a nude number because it is divisible by every one of its digits.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 239 ways as a sum of consecutive naturals, for example, 299734309 + ... + 299734379.

It is an arithmetic number, because the mean of its divisors is an integer number (86091984).

Almost surely, 2^21281138424 is an apocalyptic number.

21281138424 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 21281138424, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (41324152320).

21281138424 is an abundant number, since it is smaller than the sum of its proper divisors (61367166216).

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

21281138424 is a wasteful number, since it uses less digits than its factorization.

21281138424 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 162 (or 136 counting only the distinct ones).

The product of its digits is 24576, while the sum is 36.

The spelling of 21281138424 in words is "twenty-one billion, two hundred eighty-one million, one hundred thirty-eight thousand, four hundred twenty-four".