21572 has 6 divisors (see below), whose sum is σ = 37758. Its totient is φ = 10784.

The previous prime is 21569. The next prime is 21577. The reversal of 21572 is 27512.

It can be written as a sum of positive squares in only one way, i.e., 21316 + 256 = 146^2 + 16^2 .

It is a nialpdrome in base 16.

It is a self number, because there is not a number n which added to its sum of digits gives 21572.

It is not an unprimeable number, because it can be changed into a prime (21577) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (5) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 2693 + ... + 2700.

It is an arithmetic number, because the mean of its divisors is an integer number (6293).

2²¹⁵⁷² is an apocalyptic number.

It is an amenable number.

21572 is a deficient number, since it is larger than the sum of its proper divisors (16186).

21572 is a wasteful number, since it uses less digits than its factorization.

21572 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5397 (or 5395 counting only the distinct ones).

The product of its digits is 140, while the sum is 17.

The square root of 21572 is about 146.8740957419. The cubic root of 21572 is about 27.8374940493.

Adding to 21572 its product of digits (140), we get a palindrome (21712).

The spelling of 21572 in words is "twenty-one thousand, five hundred seventy-two".