21206530 has 8 divisors (see below), whose sum is σ = 38171772. Its totient is φ = 8482608.

The previous prime is 21206509. The next prime is 21206533. The reversal of 21206530 is 3560212.

It is a happy number.

It can be written as a sum of positive squares in 2 ways, for example, as 18983449 + 2223081 = 4357^2 + 1491^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is a junction number, because it is equal to n+sod(n) for n = 21206498 and 21206507.

It is not an unprimeable number, because it can be changed into a prime (21206533) 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, 1060317 + ... + 1060336.

Almost surely, 2^21206530 is an apocalyptic number.

21206530 is a deficient number, since it is larger than the sum of its proper divisors (16965242).

21206530 is a wasteful number, since it uses less digits than its factorization.

21206530 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2120660.

The product of its (nonzero) digits is 360, while the sum is 19.

The square root of 21206530 is about 4605.0548313782. The cubic root of 21206530 is about 276.7939141439.

Adding to 21206530 its reverse (3560212), we get a palindrome (24766742).

It can be divided in two parts, 21206 and 530, that added together give a triangular number (21736 = T₂₀₈).

The spelling of 21206530 in words is "twenty-one million, two hundred six thousand, five hundred thirty".