21305203440 has 40 divisors (see below), whose sum is σ = 66046131408. Its totient is φ = 5681387520.

The previous prime is 21305203391. The next prime is 21305203453. The reversal of 21305203440 is 4430250312.

It is a tau number, because it is divible by the number of its divisors (40).

It is a Harshad number since it is a multiple of its sum of digits (24).

It is a self number, because there is not a number n which added to its sum of digits gives 21305203440.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 44385601 + ... + 44386080.

Almost surely, 2^21305203440 is an apocalyptic number.

21305203440 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21305203440 is an abundant number, since it is smaller than the sum of its proper divisors (44740927968).

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

21305203440 is a wasteful number, since it uses less digits than its factorization.

21305203440 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 88771697 (or 88771691 counting only the distinct ones).

The product of its (nonzero) digits is 2880, while the sum is 24.

Adding to 21305203440 its reverse (4430250312), we get a palindrome (25735453752).

The spelling of 21305203440 in words is "twenty-one billion, three hundred five million, two hundred three thousand, four hundred forty".