21120 has 64 divisors (see below), whose sum is σ = 73440. Its totient is φ = 5120.

The previous prime is 21107. The next prime is 21121. The reversal of 21120 is 2112.

It is a happy number.

It is a tau number, because it is divible by the number of its divisors (64).

It is a Harshad number since it is a multiple of its sum of digits (6).

It is a super Niven number, because it is divisible the sum of any subset of its (nonzero) digits.

It is a junction number, because it is equal to n+sod(n) for n = 21099 and 21108.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21121) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 1915 + ... + 1925.

2²¹¹²⁰ is an apocalyptic number.

21120 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 21120, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (36720).

21120 is an abundant number, since it is smaller than the sum of its proper divisors (52320).

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

21120 is a wasteful number, since it uses less digits than its factorization.

21120 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 33 (or 21 counting only the distinct ones).

The product of its (nonzero) digits is 4, while the sum is 6.

The square root of 21120 is about 145.3272169967. The cubic root of 21120 is about 27.6416929200.

Adding to 21120 its reverse (2112), we get a palindrome (23232).

It can be divided in two parts, 211 and 20, that added together give a triangular number (231 = T₂₁).

The spelling of 21120 in words is "twenty-one thousand, one hundred twenty", and thus it is an iban number.