21306672 has 160 divisors (see below), whose sum is σ = 66344960. Its totient is φ = 6531840.

The previous prime is 21306617. The next prime is 21306707. The reversal of 21306672 is 27660312.

It is a happy number.

It is a Harshad number since it is a multiple of its sum of digits (27).

It is an unprimeable number.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 495483 + ... + 495525.

It is an arithmetic number, because the mean of its divisors is an integer number (414656).

Almost surely, 2^21306672 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21306672, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (33172480).

21306672 is an abundant number, since it is smaller than the sum of its proper divisors (45038288).

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

21306672 is a wasteful number, since it uses less digits than its factorization.

21306672 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 128 (or 116 counting only the distinct ones).

The product of its (nonzero) digits is 3024, while the sum is 27.

The square root of 21306672 is about 4615.9150772084. The cubic root of 21306672 is about 277.2289244756.

Adding to 21306672 its reverse (27660312), we get a palindrome (48966984).

The spelling of 21306672 in words is "twenty-one million, three hundred six thousand, six hundred seventy-two".