21318605 has 16 divisors (see below), whose sum is σ = 31895424. Its totient is φ = 13289280.

The previous prime is 21318599. The next prime is 21318643. The reversal of 21318605 is 50681312.

It is not a de Polignac number, because 21318605 - 2⁶ = 21318541 is a prime.

It is a Curzon number.

It is a plaindrome in base 13.

It is a congruent number.

It is an unprimeable number.

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 in 15 ways as a sum of consecutive naturals, for example, 27302 + ... + 28071.

It is an arithmetic number, because the mean of its divisors is an integer number (1993464).

Almost surely, 2^21318605 is an apocalyptic number.

It is an amenable number.

21318605 is a deficient number, since it is larger than the sum of its proper divisors (10576819).

21318605 is a wasteful number, since it uses less digits than its factorization.

21318605 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 55396.

The product of its (nonzero) digits is 1440, while the sum is 26.

The square root of 21318605 is about 4617.2074893814. The cubic root of 21318605 is about 277.2806696967.

Adding to 21318605 its reverse (50681312), we get a palindrome (71999917).

The spelling of 21318605 in words is "twenty-one million, three hundred eighteen thousand, six hundred five".