21131712 has 112 divisors (see below), whose sum is σ = 71038720. Its totient is φ = 6034176.

The previous prime is 21131711. The next prime is 21131713. The reversal of 21131712 is 21713112.

It is a happy number.

It is an interprime number because it is at equal distance from previous prime (21131711) and next prime (21131713).

It is a tau number, because it is divible by the number of its divisors (112).

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

It is a nude number because it is divisible by every one of its digits and also a Zuckerman number because it is divisible by the product of its digits.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21131711) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 11223 + ... + 12969.

Almost surely, 2^21131712 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 21131712, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (35519360).

21131712 is an abundant number, since it is smaller than the sum of its proper divisors (49907008).

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

21131712 is a wasteful number, since it uses less digits than its factorization.

21131712 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1775 (or 1759 counting only the distinct ones).

The product of its digits is 84, while the sum is 18.

The square root of 21131712 is about 4596.9241890638. The cubic root of 21131712 is about 276.4680150090.

Adding to 21131712 its reverse (21713112), we get a palindrome (42844824).

The spelling of 21131712 in words is "twenty-one million, one hundred thirty-one thousand, seven hundred twelve".