21240506 has 8 divisors (see below), whose sum is σ = 36412320. Its totient is φ = 9103068.

The previous prime is 21240433. The next prime is 21240511. The reversal of 21240506 is 60504212.

It is a happy number.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a Curzon 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 3 ways as a sum of consecutive naturals, for example, 758576 + ... + 758603.

It is an arithmetic number, because the mean of its divisors is an integer number (4551540).

Almost surely, 2^21240506 is an apocalyptic number.

21240506 is a deficient number, since it is larger than the sum of its proper divisors (15171814).

21240506 is a wasteful number, since it uses less digits than its factorization.

21240506 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1517188.

The product of its (nonzero) digits is 480, while the sum is 20.

The square root of 21240506 is about 4608.7423447184. The cubic root of 21240506 is about 276.9416568770.

Adding to 21240506 its reverse (60504212), we get a palindrome (81744718).

The spelling of 21240506 in words is "twenty-one million, two hundred forty thousand, five hundred six".