21372 has 24 divisors (see below), whose sum is σ = 54096. Its totient is φ = 6528.

The previous prime is 21347. The next prime is 21377. The reversal of 21372 is 27312.

It is a nialpdrome in base 13.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21377) by changing a digit.

21372 is an untouchable number, because it is not equal to the sum of proper divisors of any number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 88 + ... + 224.

It is an arithmetic number, because the mean of its divisors is an integer number (2254).

2²¹³⁷² 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 21372, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (27048).

21372 is an abundant number, since it is smaller than the sum of its proper divisors (32724).

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

21372 is a wasteful number, since it uses less digits than its factorization.

21372 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 157 (or 155 counting only the distinct ones).

The product of its digits is 84, while the sum is 15.

The square root of 21372 is about 146.1916550286. The cubic root of 21372 is about 27.7511970914.

Adding to 21372 its reverse (27312), we get a palindrome (48684).

It can be divided in two parts, 21 and 372, that added together give a palindrome (393).

The spelling of 21372 in words is "twenty-one thousand, three hundred seventy-two", and thus it is an iban number.