21109206 has 16 divisors (see below), whose sum is σ = 44702064. Its totient is φ = 6622464.

The previous prime is 21109201. The next prime is 21109217. The reversal of 21109206 is 60290112.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21109201) by changing a digit.

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 in 7 ways as a sum of consecutive naturals, for example, 103375 + ... + 103578.

It is an arithmetic number, because the mean of its divisors is an integer number (2793879).

Almost surely, 2^21109206 is an apocalyptic number.

21109206 is an abundant number, since it is smaller than the sum of its proper divisors (23592858).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21109206 is a wasteful number, since it uses less digits than its factorization.

21109206 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 206975.

The product of its (nonzero) digits is 216, while the sum is 21.

The square root of 21109206 is about 4594.4755957563. The cubic root of 21109206 is about 276.3698308297.

Adding to 21109206 its reverse (60290112), we get a palindrome (81399318).

The spelling of 21109206 in words is "twenty-one million, one hundred nine thousand, two hundred six".