21012400000 has 192 divisors, whose sum is σ = 52853335920. Its totient is φ = 8320000000.

The previous prime is 21012399997. The next prime is 21012400021. The reversal of 21012400000 is 421012.

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 21012400000.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 52399800 + ... + 52400200.

Almost surely, 2^21012400000 is an apocalyptic number.

21012400000 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 21012400000, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (26426667960).

21012400000 is an abundant number, since it is smaller than the sum of its proper divisors (31840935920).

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

21012400000 is an frugal number, since it uses more digits than its factorization.

21012400000 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 571 (or 539 counting only the distinct ones).

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

Adding to 21012400000 its reverse (421012), we get a palindrome (21012821012).

The spelling of 21012400000 in words is "twenty-one billion, twelve million, four hundred thousand".