21489231780 has 144 divisors (see below), whose sum is σ = 65654971200. Its totient is φ = 5689232640.

The previous prime is 21489231779. The next prime is 21489231787. The reversal of 21489231780 is 8713298412.

It is a happy number.

It is a Harshad number since it is a multiple of its sum of digits (45).

It is not an unprimeable number, because it can be changed into a prime (21489231787) by changing a digit.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 18350595 + ... + 18351765.

It is an arithmetic number, because the mean of its divisors is an integer number (455937300).

Almost surely, 2^21489231780 is an apocalyptic number.

21489231780 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 21489231780, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (32827485600).

21489231780 is an abundant number, since it is smaller than the sum of its proper divisors (44165739420).

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

21489231780 is a wasteful number, since it uses less digits than its factorization.

21489231780 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1834 (or 1829 counting only the distinct ones).

The product of its (nonzero) digits is 193536, while the sum is 45.

The spelling of 21489231780 in words is "twenty-one billion, four hundred eighty-nine million, two hundred thirty-one thousand, seven hundred eighty".