21155444424 has 48 divisors (see below), whose sum is σ = 57311486700. Its totient is φ = 7049908224.

The previous prime is 21155444423. The next prime is 21155444441. The reversal of 21155444424 is 42444455112.

21155444424 is a `hidden beast` number, since 21 + 1 + 554 + 44 + 42 + 4 = 666.

It can be written as a sum of positive squares in 2 ways, for example, as 18058521924 + 3096922500 = 134382^2 + 55650^2 .

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

It is not an unprimeable number, because it can be changed into a prime (21155444423) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 242232 + ... + 317784.

Almost surely, 2^21155444424 is an apocalyptic number.

21155444424 is a gapful number since it is divisible by the number (24) formed by its first and last digit.

It is an amenable number.

21155444424 is an abundant number, since it is smaller than the sum of its proper divisors (36156042276).

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

21155444424 is a wasteful number, since it uses less digits than its factorization.

21155444424 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 79454 (or 79447 counting only the distinct ones).

The product of its digits is 102400, while the sum is 36.

Adding to 21155444424 its reverse (42444455112), we get a palindrome (63599899536).

The spelling of 21155444424 in words is "twenty-one billion, one hundred fifty-five million, four hundred forty-four thousand, four hundred twenty-four".