21172732 has 48 divisors (see below), whose sum is σ = 44126208. Its totient is φ = 8700480.

The previous prime is 21172717. The next prime is 21172733. The reversal of 21172732 is 23727112.

It is a junction number, because it is equal to n+sod(n) for n = 21172697 and 21172706.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21172733) 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, 110757 + ... + 110947.

It is an arithmetic number, because the mean of its divisors is an integer number (919296).

Almost surely, 2^21172732 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 21172732, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (22063104).

21172732 is an abundant number, since it is smaller than the sum of its proper divisors (22953476).

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

21172732 is a wasteful number, since it uses less digits than its factorization.

21172732 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 346 (or 344 counting only the distinct ones).

The product of its digits is 1176, while the sum is 25.

The square root of 21172732 is about 4601.3837049305. The cubic root of 21172732 is about 276.6467887849.

Adding to 21172732 its reverse (23727112), we get a palindrome (44899844).

It can be divided in two parts, 21172 and 732, that added together give a square (21904 = 148²).

The spelling of 21172732 in words is "twenty-one million, one hundred seventy-two thousand, seven hundred thirty-two".