21306206 has 4 divisors (see below), whose sum is σ = 31959312. Its totient is φ = 10653102.

The previous prime is 21306193. The next prime is 21306209. The reversal of 21306206 is 60260312.

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

It is a super-2 number, since 2×21306206² = 907908828228872, which contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21306209) 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 as a sum of consecutive naturals, namely, 5326550 + ... + 5326553.

It is an arithmetic number, because the mean of its divisors is an integer number (7989828).

Almost surely, 2^21306206 is an apocalyptic number.

21306206 is a deficient number, since it is larger than the sum of its proper divisors (10653106).

21306206 is a wasteful number, since it uses less digits than its factorization.

21306206 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 10653105.

The product of its (nonzero) digits is 432, while the sum is 20.

The square root of 21306206 is about 4615.8645994006. The cubic root of 21306206 is about 277.2269033619.

Adding to 21306206 its reverse (60260312), we get a palindrome (81566518).

It can be divided in two parts, 21306 and 206, that added together give a palindrome (21512).

The spelling of 21306206 in words is "twenty-one million, three hundred six thousand, two hundred six".