21131042440 has 32 divisors (see below), whose sum is σ = 47615552280. Its totient is φ = 8439846912.

The previous prime is 21131042437. The next prime is 21131042441. The reversal of 21131042440 is 4424013112.

It is a happy number.

It can be written as a sum of positive squares in 4 ways, for example, as 16213947556 + 4917094884 = 127334^2 + 70122^2 .

It is not an unprimeable number, because it can be changed into a prime (21131042441) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 365559 + ... + 419398.

Almost surely, 2^21131042440 is an apocalyptic number.

21131042440 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21131042440 is an abundant number, since it is smaller than the sum of its proper divisors (26484509840).

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

21131042440 is a wasteful number, since it uses less digits than its factorization.

21131042440 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 785641 (or 785637 counting only the distinct ones).

The product of its (nonzero) digits is 768, while the sum is 22.

Adding to 21131042440 its reverse (4424013112), we get a palindrome (25555055552).

The spelling of 21131042440 in words is "twenty-one billion, one hundred thirty-one million, forty-two thousand, four hundred forty".