21681180 has 72 divisors (see below), whose sum is σ = 68638752. Its totient is φ = 5529216.

The previous prime is 21681173. The next prime is 21681193. The reversal of 21681180 is 8118612.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 1522 + ... + 6758.

It is an arithmetic number, because the mean of its divisors is an integer number (953316).

Almost surely, 2^21681180 is an apocalyptic number.

21681180 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 21681180, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (34319376).

21681180 is an abundant number, since it is smaller than the sum of its proper divisors (46957572).

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

21681180 is a wasteful number, since it uses less digits than its factorization.

21681180 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5275 (or 5270 counting only the distinct ones).

The product of its (nonzero) digits is 768, while the sum is 27.

The square root of 21681180 is about 4656.3054023550. The cubic root of 21681180 is about 278.8437866027.

Adding to 21681180 its reverse (8118612), we get a palindrome (29799792).

The spelling of 21681180 in words is "twenty-one million, six hundred eighty-one thousand, one hundred eighty".