21684989440 has 80 divisors (see below), whose sum is σ = 53202563568. Its totient is φ = 8472231936.

The previous prime is 21684989419. The next prime is 21684989441. The reversal of 21684989440 is 4498948612.

It is a happy number.

It is a tau number, because it is divible by the number of its divisors (80).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21684989441) 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, 11584 + ... + 208576.

Almost surely, 2^21684989440 is an apocalyptic number.

21684989440 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21684989440, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (26601281784).

21684989440 is an abundant number, since it is smaller than the sum of its proper divisors (31517574128).

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

21684989440 is an equidigital number, since it uses as much as digits as its factorization.

21684989440 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 197059 (or 197043 counting only the distinct ones).

The product of its (nonzero) digits is 3981312, while the sum is 55.

The spelling of 21684989440 in words is "twenty-one billion, six hundred eighty-four million, nine hundred eighty-nine thousand, four hundred forty".