21308672 has 144 divisors (see below), whose sum is σ = 56512512. Its totient is φ = 7772160.

The previous prime is 21308663. The next prime is 21308681. The reversal of 21308672 is 27680312.

It is a happy number.

It is an interprime number because it is at equal distance from previous prime (21308663) and next prime (21308681).

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 453353 + ... + 453399.

It is an arithmetic number, because the mean of its divisors is an integer number (392448).

Almost surely, 2^21308672 is an apocalyptic number.

21308672 is a gapful number since it is divisible by the number (22) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21308672, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (28256256).

21308672 is an abundant number, since it is smaller than the sum of its proper divisors (35203840).

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

21308672 is a wasteful number, since it uses less digits than its factorization.

21308672 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 104 (or 90 counting only the distinct ones).

The product of its (nonzero) digits is 4032, while the sum is 29.

The square root of 21308672 is about 4616.1317138921. The cubic root of 21308672 is about 277.2375984488.

Adding to 21308672 its reverse (27680312), we get a palindrome (48988984).

The spelling of 21308672 in words is "twenty-one million, three hundred eight thousand, six hundred seventy-two".