21206120 has 48 divisors (see below), whose sum is σ = 51682860. Its totient is φ = 7827456.

The previous prime is 21206117. The next prime is 21206131. The reversal of 21206120 is 2160212.

It can be written as a sum of positive squares in 6 ways, for example, as 8773444 + 12432676 = 2962^2 + 3526^2 .

It is a junction number, because it is equal to n+sod(n) for n = 21206095 and 21206104.

It is an unprimeable number.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 5192 + ... + 8328.

Almost surely, 2^21206120 is an apocalyptic number.

21206120 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 21206120, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (25841430).

21206120 is an abundant number, since it is smaller than the sum of its proper divisors (30476740).

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

21206120 is a wasteful number, since it uses less digits than its factorization.

21206120 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3174 (or 3157 counting only the distinct ones).

The product of its (nonzero) digits is 48, while the sum is 14.

The square root of 21206120 is about 4605.0103148636. The cubic root of 21206120 is about 276.7921303185.

Adding to 21206120 its reverse (2160212), we get a palindrome (23366332).

The spelling of 21206120 in words is "twenty-one million, two hundred six thousand, one hundred twenty".