21530217180 has 96 divisors (see below), whose sum is σ = 61366697280. Its totient is φ = 5638625280.

The previous prime is 21530217173. The next prime is 21530217221. The reversal of 21530217180 is 8171203512.

It is a Harshad number since it is a multiple of its sum of digits (30).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 2590792 + ... + 2599088.

It is an arithmetic number, because the mean of its divisors is an integer number (639236430).

Almost surely, 2^21530217180 is an apocalyptic number.

21530217180 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 21530217180, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (30683348640).

21530217180 is an abundant number, since it is smaller than the sum of its proper divisors (39836480100).

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

21530217180 is a wasteful number, since it uses less digits than its factorization.

21530217180 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 9079 (or 9077 counting only the distinct ones).

The product of its (nonzero) digits is 3360, while the sum is 30.

The spelling of 21530217180 in words is "twenty-one billion, five hundred thirty million, two hundred seventeen thousand, one hundred eighty".