21021206 has 8 divisors (see below), whose sum is σ = 31568880. Its totient is φ = 10498248.

The previous prime is 21021181. The next prime is 21021229. The reversal of 21021206 is 60212012.

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

It is a super-2 number, since 2×21021206² = 883782203388872, which contains 22 as substring.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 3881 + ... + 7556.

It is an arithmetic number, because the mean of its divisors is an integer number (3946110).

Almost surely, 2^21021206 is an apocalyptic number.

21021206 is a deficient number, since it is larger than the sum of its proper divisors (10547674).

21021206 is a wasteful number, since it uses less digits than its factorization.

21021206 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 12358.

The product of its (nonzero) digits is 48, while the sum is 14.

The square root of 21021206 is about 4584.8888754254. Note that the first 4 decimals coincide. The cubic root of 21021206 is about 275.9852526602.

Adding to 21021206 its reverse (60212012), we get a palindrome (81233218).

The spelling of 21021206 in words is "twenty-one million, twenty-one thousand, two hundred six".