21242605 has 16 divisors (see below), whose sum is σ = 27324864. Its totient is φ = 15796480.

The previous prime is 21242591. The next prime is 21242629. The reversal of 21242605 is 50624212.

It is not a de Polignac number, because 21242605 - 2⁹ = 21242093 is a prime.

It is a Duffinian number.

It is a congruent number.

It is an unprimeable number.

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 15 ways as a sum of consecutive naturals, for example, 5550 + ... + 8560.

It is an arithmetic number, because the mean of its divisors is an integer number (1707804).

Almost surely, 2^21242605 is an apocalyptic number.

It is an amenable number.

21242605 is a deficient number, since it is larger than the sum of its proper divisors (6082259).

21242605 is a wasteful number, since it uses less digits than its factorization.

21242605 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3116.

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

The square root of 21242605 is about 4608.9700584838. The cubic root of 21242605 is about 276.9507790920.

Adding to 21242605 its reverse (50624212), we get a palindrome (71866817).

The spelling of 21242605 in words is "twenty-one million, two hundred forty-two thousand, six hundred five".