21205246 has 4 divisors (see below), whose sum is σ = 31807872. Its totient is φ = 10602622.

The previous prime is 21205243. The next prime is 21205279. The reversal of 21205246 is 64250212.

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

It is a Smith number, since the sum of its digits (22) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21205243) 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, 5301310 + ... + 5301313.

It is an arithmetic number, because the mean of its divisors is an integer number (7951968).

Almost surely, 2^21205246 is an apocalyptic number.

21205246 is a deficient number, since it is larger than the sum of its proper divisors (10602626).

21205246 is a wasteful number, since it uses less digits than its factorization.

21205246 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 10602625.

The product of its (nonzero) digits is 960, while the sum is 22.

The square root of 21205246 is about 4604.9154172471. The cubic root of 21205246 is about 276.7883276483.

Adding to 21205246 its reverse (64250212), we get a palindrome (85455458).

The spelling of 21205246 in words is "twenty-one million, two hundred five thousand, two hundred forty-six".