21206320 has 20 divisors (see below), whose sum is σ = 49304880. Its totient is φ = 8482496.

The previous prime is 21206303. The next prime is 21206323. The reversal of 21206320 is 2360212.

It is a tau number, because it is divible by the number of its divisors (20).

It is a Harshad number since it is a multiple of its sum of digits (16).

It is a junction number, because it is equal to n+sod(n) for n = 21206294 and 21206303.

It is not an unprimeable number, because it can be changed into a prime (21206323) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 132460 + ... + 132619.

It is an arithmetic number, because the mean of its divisors is an integer number (2465244).

Almost surely, 2^21206320 is an apocalyptic number.

21206320 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21206320 is an abundant number, since it is smaller than the sum of its proper divisors (28098560).

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

21206320 is a wasteful number, since it uses less digits than its factorization.

21206320 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 265092 (or 265086 counting only the distinct ones).

The product of its (nonzero) digits is 144, while the sum is 16.

The square root of 21206320 is about 4605.0320302903. The cubic root of 21206320 is about 276.7930004801.

Adding to 21206320 its reverse (2360212), we get a palindrome (23566532).

The spelling of 21206320 in words is "twenty-one million, two hundred six thousand, three hundred twenty".