21207530 has 8 divisors (see below), whose sum is σ = 38173572. Its totient is φ = 8483008.

The previous prime is 21207509. The next prime is 21207533. The reversal of 21207530 is 3570212.

It can be written as a sum of positive squares in 2 ways, for example, as 17330569 + 3876961 = 4163^2 + 1969^2 .

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

It is a super-3 number, since 3×21207530³ (a number of 23 digits) contains 333 as substring.

It is not an unprimeable number, because it can be changed into a prime (21207533) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1060367 + ... + 1060386.

Almost surely, 2^21207530 is an apocalyptic number.

21207530 is a deficient number, since it is larger than the sum of its proper divisors (16966042).

21207530 is a wasteful number, since it uses less digits than its factorization.

21207530 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2120760.

The product of its (nonzero) digits is 420, while the sum is 20.

The square root of 21207530 is about 4605.1634064385. The cubic root of 21207530 is about 276.7982648409.

Adding to 21207530 its reverse (3570212), we get a palindrome (24777742).

The spelling of 21207530 in words is "twenty-one million, two hundred seven thousand, five hundred thirty".