21004012800 has 540 divisors, whose sum is σ = 80227948416. Its totient is φ = 5416243200.

The previous prime is 21004012793. The next prime is 21004012811. The reversal of 21004012800 is 821040012.

It is a tau number, because it is divible by the number of its divisors (540).

It is a Harshad number since it is a multiple of its sum of digits (18).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 59 ways as a sum of consecutive naturals, for example, 16069747 + ... + 16071053.

Almost surely, 2^21004012800 is an apocalyptic number.

21004012800 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 21004012800, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (40113974208).

21004012800 is an abundant number, since it is smaller than the sum of its proper divisors (59223935616).

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

21004012800 is a wasteful number, since it uses less digits than its factorization.

21004012800 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1376 (or 1348 counting only the distinct ones).

The product of its (nonzero) digits is 128, while the sum is 18.

Adding to 21004012800 its reverse (821040012), we get a palindrome (21825052812).

The spelling of 21004012800 in words is "twenty-one billion, four million, twelve thousand, eight hundred".