21072180 has 96 divisors (see below), whose sum is σ = 63552384. Its totient is φ = 5197824.

The previous prime is 21072169. The next prime is 21072187. The reversal of 21072180 is 8127012.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21072187) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 74319 + ... + 74601.

It is an arithmetic number, because the mean of its divisors is an integer number (662004).

Almost surely, 2^21072180 is an apocalyptic number.

21072180 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 21072180, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (31776192).

21072180 is an abundant number, since it is smaller than the sum of its proper divisors (42480204).

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

21072180 is a wasteful number, since it uses less digits than its factorization.

21072180 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 385 (or 383 counting only the distinct ones).

The product of its (nonzero) digits is 224, while the sum is 21.

The square root of 21072180 is about 4590.4444229290. Note that the first 4 decimals coincide. The cubic root of 21072180 is about 276.2081500590.

Adding to 21072180 its reverse (8127012), we get a palindrome (29199192).

It can be divided in two parts, 210 and 72180, that added together give a triangular number (72390 = T₃₈₀).

The spelling of 21072180 in words is "twenty-one million, seventy-two thousand, one hundred eighty".