21243400040 has 64 divisors (see below), whose sum is σ = 48551000400. Its totient is φ = 8363907072.

The previous prime is 21243400033. The next prime is 21243400051. The reversal of 21243400040 is 4000434212.

It can be written as a sum of positive squares in 8 ways, for example, as 5888720644 + 15354679396 = 76738^2 + 123914^2 .

It is a Harshad number since it is a multiple of its sum of digits (20).

It is a junction number, because it is equal to n+sod(n) for n = 21243399985 and 21243400021.

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 15 ways as a sum of consecutive naturals, for example, 1479134 + ... + 1493426.

Almost surely, 2^21243400040 is an apocalyptic number.

21243400040 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 21243400040, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (24275500200).

21243400040 is an abundant number, since it is smaller than the sum of its proper divisors (27307600360).

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

21243400040 is a wasteful number, since it uses less digits than its factorization.

21243400040 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 14886 (or 14882 counting only the distinct ones).

The product of its (nonzero) digits is 768, while the sum is 20.

Adding to 21243400040 its reverse (4000434212), we get a palindrome (25243834252).

The spelling of 21243400040 in words is "twenty-one billion, two hundred forty-three million, four hundred thousand, forty".