21004040400 has 240 divisors, whose sum is σ = 77079888000. Its totient is φ = 4789370880.

The previous prime is 21004040389. The next prime is 21004040417. The reversal of 21004040400 is 404040012.

It is a tau number, because it is divible by the number of its divisors (240).

It is a Harshad number since it is a multiple of its sum of digits (15).

It is a self number, because there is not a number n which added to its sum of digits gives 21004040400.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 3768816 + ... + 3774384.

It is an arithmetic number, because the mean of its divisors is an integer number (321166200).

Almost surely, 2^21004040400 is an apocalyptic number.

21004040400 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 21004040400, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (38539944000).

21004040400 is an abundant number, since it is smaller than the sum of its proper divisors (56075847600).

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

21004040400 is a wasteful number, since it uses less digits than its factorization.

21004040400 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 6046 (or 6035 counting only the distinct ones).

The product of its (nonzero) digits is 128, while the sum is 15.

Adding to 21004040400 its reverse (404040012), we get a palindrome (21408080412).

The spelling of 21004040400 in words is "twenty-one billion, four million, forty thousand, four hundred".