21072312 has 80 divisors (see below), whose sum is σ = 60984000. Its totient is φ = 6791040.

The previous prime is 21072307. The next prime is 21072329. The reversal of 21072312 is 21327012.

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

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 19 ways as a sum of consecutive naturals, for example, 19564 + ... + 20612.

It is an arithmetic number, because the mean of its divisors is an integer number (762300).

Almost surely, 2^21072312 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 21072312, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (30492000).

21072312 is an abundant number, since it is smaller than the sum of its proper divisors (39911688).

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

21072312 is a wasteful number, since it uses less digits than its factorization.

21072312 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1098 (or 1085 counting only the distinct ones).

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

The square root of 21072312 is about 4590.4588005993. The cubic root of 21072312 is about 276.2087267973.

Adding to 21072312 its reverse (21327012), we get a palindrome (42399324).

The spelling of 21072312 in words is "twenty-one million, seventy-two thousand, three hundred twelve".