21000120 has 64 divisors (see below), whose sum is σ = 63504000. Its totient is φ = 5555328.

The previous prime is 21000103. The next prime is 21000121. The reversal of 21000120 is 2100012.

It is a happy number.

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 = 21000099 and 21000108.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21000121) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 16051 + ... + 17309.

It is an arithmetic number, because the mean of its divisors is an integer number (992250).

Almost surely, 2^21000120 is an apocalyptic number.

21000120 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 21000120, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (31752000).

21000120 is an abundant number, since it is smaller than the sum of its proper divisors (42503880).

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

21000120 is a wasteful number, since it uses less digits than its factorization.

21000120 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1412 (or 1408 counting only the distinct ones).

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

The square root of 21000120 is about 4582.5887880105. The cubic root of 21000120 is about 275.8929431465.

Adding to 21000120 its reverse (2100012), we get a palindrome (23100132).

The spelling of 21000120 in words is "twenty-one million, one hundred twenty", and thus it is an aban number.