21243400440 has 64 divisors (see below), whose sum is σ = 64053776160. Its totient is φ = 5636144640.

The previous prime is 21243400439. The next prime is 21243400459. The reversal of 21243400440 is 4400434212.

It is a happy number.

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 21243400440.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 425671 + ... + 472950.

Almost surely, 2^21243400440 is an apocalyptic number.

21243400440 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21243400440 is an abundant number, since it is smaller than the sum of its proper divisors (42810375720).

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

21243400440 is a wasteful number, since it uses less digits than its factorization.

21243400440 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 898832 (or 898828 counting only the distinct ones).

The product of its (nonzero) digits is 3072, while the sum is 24.

Adding to 21243400440 its reverse (4400434212), we get a palindrome (25643834652).

The spelling of 21243400440 in words is "twenty-one billion, two hundred forty-three million, four hundred thousand, four hundred forty".