21101220180 has 144 divisors (see below), whose sum is σ = 64948875264. Its totient is φ = 5544806400.

The previous prime is 21101220167. The next prime is 21101220181. The reversal of 21101220180 is 8102210112.

It is a super-2 number, since 2×21101220180² (a number of 21 digits) contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (18).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21101220181) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 3448804 + ... + 3454916.

It is an arithmetic number, because the mean of its divisors is an integer number (451033856).

Almost surely, 2^21101220180 is an apocalyptic number.

21101220180 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 21101220180, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (32474437632).

21101220180 is an abundant number, since it is smaller than the sum of its proper divisors (43847655084).

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

21101220180 is a wasteful number, since it uses less digits than its factorization.

21101220180 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 6406 (or 6401 counting only the distinct ones).

The product of its (nonzero) digits is 64, while the sum is 18.

Adding to 21101220180 its reverse (8102210112), we get a palindrome (29203430292).

The spelling of 21101220180 in words is "twenty-one billion, one hundred one million, two hundred twenty thousand, one hundred eighty".