21207312 has 80 divisors (see below), whose sum is σ = 69578880. Its totient is φ = 6058368.

The previous prime is 21207301. The next prime is 21207331. The reversal of 21207312 is 21370212.

It is a Harshad number since it is a multiple of its sum of digits (18).

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 483 + ... + 6530.

It is an arithmetic number, because the mean of its divisors is an integer number (869736).

Almost surely, 2^21207312 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 21207312, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (34789440).

21207312 is an abundant number, since it is smaller than the sum of its proper divisors (48371568).

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

21207312 is a wasteful number, since it uses less digits than its factorization.

21207312 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7037 (or 7025 counting only the distinct ones).

The product of its (nonzero) digits is 168, while the sum is 18.

The square root of 21207312 is about 4605.1397372935. The cubic root of 21207312 is about 276.7973164006.

Adding to 21207312 its reverse (21370212), we get a palindrome (42577524).

The spelling of 21207312 in words is "twenty-one million, two hundred seven thousand, three hundred twelve".