21573 has 16 divisors (see below), whose sum is σ = 34560. Its totient is φ = 13248.
The previous prime is 21569. The next prime is 21577. The reversal of 21573 is 37512.
21573 is nontrivially palindromic in base 16.
It is an interprime number because it is at equal distance from previous prime (21569) and next prime (21577).
It is not a de Polignac number, because 21573 - 22 = 21569 is a prime.
It is a congruent number.
It is not an unprimeable number, because it can be changed into a prime (21577) 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, 436 + ... + 482.
It is an arithmetic number, because the mean of its divisors is an integer number (2160).
221573 is an apocalyptic number.
It is an amenable number.
21573 is a deficient number, since it is larger than the sum of its proper divisors (12987).
21573 is a wasteful number, since it uses less digits than its factorization.
21573 is an evil number, because the sum of its binary digits is even.
The sum of its prime factors is 73 (or 67 counting only the distinct ones).
The product of its digits is 210, while the sum is 18.
The square root of 21573 is about 146.8774999787. The cubic root of 21573 is about 27.8379241912.
The spelling of 21573 in words is "twenty-one thousand, five hundred seventy-three".
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