21138438888 has 384 divisors, whose sum is σ = 70153776000. Its totient is φ = 5878656000.

The previous prime is 21138438887. The next prime is 21138438901. The reversal of 21138438888 is 88883483112.

It is a Harshad number since it is a multiple of its sum of digits (54).

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

It is not an unprimeable number, because it can be changed into a prime (21138438887) by changing a digit.

It is a polite number, since it can be written in 95 ways as a sum of consecutive naturals, for example, 84216763 + ... + 84217013.

It is an arithmetic number, because the mean of its divisors is an integer number (182692125).

Almost surely, 2^21138438888 is an apocalyptic number.

21138438888 is a gapful number since it is divisible by the number (28) 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 21138438888, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (35076888000).

21138438888 is an abundant number, since it is smaller than the sum of its proper divisors (49015337112).

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

21138438888 is a wasteful number, since it uses less digits than its factorization.

21138438888 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 462 (or 445 counting only the distinct ones).

The product of its digits is 2359296, while the sum is 54.

The spelling of 21138438888 in words is "twenty-one billion, one hundred thirty-eight million, four hundred thirty-eight thousand, eight hundred eighty-eight".