21306318 has 32 divisors (see below), whose sum is σ = 47371392. Its totient is φ = 6333600.

The previous prime is 21306317. The next prime is 21306343. The reversal of 21306318 is 81360312.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21306317) 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 in 15 ways as a sum of consecutive naturals, for example, 453 + ... + 6543.

It is an arithmetic number, because the mean of its divisors is an integer number (1480356).

Almost surely, 2^21306318 is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21306318, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (23685696).

21306318 is an abundant number, since it is smaller than the sum of its proper divisors (26065074).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21306318 is a wasteful number, since it uses less digits than its factorization.

21306318 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 6160.

The product of its (nonzero) digits is 864, while the sum is 24.

The square root of 21306318 is about 4615.8767314563. The cubic root of 21306318 is about 277.2273891258.

It can be divided in two parts, 2130 and 6318, that added together give a palindrome (8448).

The spelling of 21306318 in words is "twenty-one million, three hundred six thousand, three hundred eighteen".