21144400440 has 32 divisors (see below), whose sum is σ = 63433201680. Its totient is φ = 5638506752.

The previous prime is 21144400391. The next prime is 21144400451. The reversal of 21144400440 is 4400444112.

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 21144400440.

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, 88101549 + ... + 88101788.

Almost surely, 2^21144400440 is an apocalyptic number.

21144400440 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21144400440 is an abundant number, since it is smaller than the sum of its proper divisors (42288801240).

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

21144400440 is a wasteful number, since it uses less digits than its factorization.

21144400440 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 176203351 (or 176203347 counting only the distinct ones).

The product of its (nonzero) digits is 2048, while the sum is 24.

Adding to 21144400440 its reverse (4400444112), we get a palindrome (25544844552).

The spelling of 21144400440 in words is "twenty-one billion, one hundred forty-four million, four hundred thousand, four hundred forty".