21720160 has 192 divisors, whose sum is σ = 67060224. Its totient is φ = 6451200.

The previous prime is 21720137. The next prime is 21720197. The reversal of 21720160 is 6102712.

It is a zygodrome in base 9.

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 31 ways as a sum of consecutive naturals, for example, 505099 + ... + 505141.

It is an arithmetic number, because the mean of its divisors is an integer number (349272).

Almost surely, 2^21720160 is an apocalyptic number.

21720160 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 21720160, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (33530112).

21720160 is an abundant number, since it is smaller than the sum of its proper divisors (45340064).

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

21720160 is a wasteful number, since it uses less digits than its factorization.

21720160 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 117 (or 109 counting only the distinct ones).

The product of its (nonzero) digits is 168, while the sum is 19.

The square root of 21720160 is about 4660.4892447038. The cubic root of 21720160 is about 279.0107950928.

Adding to 21720160 its reverse (6102712), we get a palindrome (27822872).

The spelling of 21720160 in words is "twenty-one million, seven hundred twenty thousand, one hundred sixty".