21543402400 has 72 divisors (see below), whose sum is σ = 56638460844. Its totient is φ = 7954483200.

The previous prime is 21543402379. The next prime is 21543402407. The reversal of 21543402400 is 420434512.

It is a happy number.

It can be written as a sum of positive squares in 6 ways, for example, as 6134648976 + 15408753424 = 78324^2 + 124132^2 .

It is a Harshad number since it is a multiple of its sum of digits (25).

It is not an unprimeable number, because it can be changed into a prime (21543402407) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 1025341 + ... + 1046140.

Almost surely, 2^21543402400 is an apocalyptic number.

21543402400 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21543402400 is an abundant number, since it is smaller than the sum of its proper divisors (35095058444).

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

21543402400 is a wasteful number, since it uses less digits than its factorization.

21543402400 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2071514 (or 2071501 counting only the distinct ones).

The product of its (nonzero) digits is 3840, while the sum is 25.

Adding to 21543402400 its reverse (420434512), we get a palindrome (21963836912).

The spelling of 21543402400 in words is "twenty-one billion, five hundred forty-three million, four hundred two thousand, four hundred".