21530206 has 4 divisors (see below), whose sum is σ = 32295312. Its totient is φ = 10765102.

The previous prime is 21530161. The next prime is 21530227. The reversal of 21530206 is 60203512.

It is a happy number.

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

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 5382550 + ... + 5382553.

It is an arithmetic number, because the mean of its divisors is an integer number (8073828).

Almost surely, 2^21530206 is an apocalyptic number.

21530206 is a deficient number, since it is larger than the sum of its proper divisors (10765106).

21530206 is a wasteful number, since it uses less digits than its factorization.

21530206 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 10765105.

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

The square root of 21530206 is about 4640.0653012646. The cubic root of 21530206 is about 278.1950479794.

Adding to 21530206 its reverse (60203512), we get a palindrome (81733718).

It can be divided in two parts, 21530 and 206, that added together give a triangular number (21736 = T₂₀₈).

The spelling of 21530206 in words is "twenty-one million, five hundred thirty thousand, two hundred six".