21120400000 has 384 divisors, whose sum is σ = 63427190400. Its totient is φ = 6842880000.

The previous prime is 21120399997. The next prime is 21120400013. The reversal of 21120400000 is 402112.

It is a Harshad number since it is a multiple of its sum of digits (10).

It is a self number, because there is not a number n which added to its sum of digits gives 21120400000.

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 47 ways as a sum of consecutive naturals, for example, 53199802 + ... + 53200198.

It is an arithmetic number, because the mean of its divisors is an integer number (165174975).

Almost surely, 2^21120400000 is an apocalyptic number.

21120400000 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 21120400000, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (31713595200).

21120400000 is an abundant number, since it is smaller than the sum of its proper divisors (42306790400).

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

21120400000 is an frugal number, since it uses more digits than its factorization.

21120400000 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 462 (or 430 counting only the distinct ones).

The product of its (nonzero) digits is 16, while the sum is 10.

Adding to 21120400000 its reverse (402112), we get a palindrome (21120802112).

The spelling of 21120400000 in words is "twenty-one billion, one hundred twenty million, four hundred thousand".