21105206 has 4 divisors (see below), whose sum is σ = 31657812. Its totient is φ = 10552602.

The previous prime is 21105199. The next prime is 21105221. The reversal of 21105206 is 60250112.

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 polite number, since it can be written as a sum of consecutive naturals, namely, 5276300 + ... + 5276303.

It is an arithmetic number, because the mean of its divisors is an integer number (7914453).

Almost surely, 2^21105206 is an apocalyptic number.

21105206 is a deficient number, since it is larger than the sum of its proper divisors (10552606).

21105206 is a wasteful number, since it uses less digits than its factorization.

21105206 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 10552605.

The product of its (nonzero) digits is 120, while the sum is 17.

The square root of 21105206 is about 4594.0402697408. The cubic root of 21105206 is about 276.3523732150.

Adding to 21105206 its reverse (60250112), we get a palindrome (81355318).

The spelling of 21105206 in words is "twenty-one million, one hundred five thousand, two hundred six".