21242105 has 4 divisors (see below), whose sum is σ = 25490532. Its totient is φ = 16993680.

The previous prime is 21242101. The next prime is 21242131. The reversal of 21242105 is 50124212.

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

It can be written as a sum of positive squares in 2 ways, for example, as 5812921 + 15429184 = 2411^2 + 3928^2 .

It is not a de Polignac number, because 21242105 - 2² = 21242101 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21242101) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2124206 + ... + 2124215.

It is an arithmetic number, because the mean of its divisors is an integer number (6372633).

Almost surely, 2^21242105 is an apocalyptic number.

It is an amenable number.

21242105 is a deficient number, since it is larger than the sum of its proper divisors (4248427).

21242105 is an equidigital number, since it uses as much as digits as its factorization.

21242105 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4248426.

The product of its (nonzero) digits is 160, while the sum is 17.

The square root of 21242105 is about 4608.9158161112. The cubic root of 21242105 is about 276.9486061558.

Adding to 21242105 its reverse (50124212), we get a palindrome (71366317).

The spelling of 21242105 in words is "twenty-one million, two hundred forty-two thousand, one hundred five".