21402026440 has 64 divisors (see below), whose sum is σ = 48480410160. Its totient is φ = 8503004160.

The previous prime is 21402026431. The next prime is 21402026441. The reversal of 21402026440 is 4462020412.

It is a happy number.

It can be written as a sum of positive squares in 8 ways, for example, as 2574344644 + 18827681796 = 50738^2 + 137214^2 .

It is not an unprimeable number, because it can be changed into a prime (21402026441) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 8780902 + ... + 8783338.

Almost surely, 2^21402026440 is an apocalyptic number.

21402026440 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21402026440 is an abundant number, since it is smaller than the sum of its proper divisors (27078383720).

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

21402026440 is a wasteful number, since it uses less digits than its factorization.

21402026440 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3842 (or 3838 counting only the distinct ones).

The product of its (nonzero) digits is 3072, while the sum is 25.

Adding to 21402026440 its reverse (4462020412), we get a palindrome (25864046852).

The spelling of 21402026440 in words is "twenty-one billion, four hundred two million, twenty-six thousand, four hundred forty".