21312072 has 96 divisors (see below), whose sum is σ = 63117600. Its totient is φ = 6718464.

The previous prime is 21312059. The next prime is 21312077. The reversal of 21312072 is 27021312.

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

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21312077) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 36648 + ... + 37224.

It is an arithmetic number, because the mean of its divisors is an integer number (657475).

Almost surely, 2^21312072 is an apocalyptic number.

It is a pronic number, being equal to 4616×4617.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21312072, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (31558800).

21312072 is an abundant number, since it is smaller than the sum of its proper divisors (41805528).

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

21312072 is a wasteful number, since it uses less digits than its factorization.

21312072 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 617 (or 601 counting only the distinct ones).

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

The square root of 21312072 is about 4616.4999729232. The cubic root of 21312072 is about 277.2523429576.

Adding to 21312072 its reverse (27021312), we get a palindrome (48333384).

The spelling of 21312072 in words is "twenty-one million, three hundred twelve thousand, seventy-two".