21530506 has 4 divisors (see below), whose sum is σ = 32295762. Its totient is φ = 10765252.

The previous prime is 21530497. The next prime is 21530513. The reversal of 21530506 is 60503512.

It is a happy number.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in only one way, i.e., 13068225 + 8462281 = 3615^2 + 2909^2 .

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 5382625 + ... + 5382628.

Almost surely, 2^21530506 is an apocalyptic number.

21530506 is a deficient number, since it is larger than the sum of its proper divisors (10765256).

21530506 is a wasteful number, since it uses less digits than its factorization.

21530506 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 10765255.

The product of its (nonzero) digits is 900, while the sum is 22.

The square root of 21530506 is about 4640.0976282833. The cubic root of 21530506 is about 278.1963400885.

The spelling of 21530506 in words is "twenty-one million, five hundred thirty thousand, five hundred six".