21571 has 8 divisors (see below), whose sum is σ = 24624. Its totient is φ = 18720.

The previous prime is 21569. The next prime is 21577. The reversal of 21571 is 17512.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 21571 - 2¹ = 21569 is a prime.

It is a Duffinian number.

21571 is a lucky number.

It is a nialpdrome in base 16.

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 7 ways as a sum of consecutive naturals, for example, 381 + ... + 433.

It is an arithmetic number, because the mean of its divisors is an integer number (3078).

2²¹⁵⁷¹ is an apocalyptic number.

21571 is a deficient number, since it is larger than the sum of its proper divisors (3053).

21571 is a wasteful number, since it uses less digits than its factorization.

21571 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 101.

The product of its digits is 70, while the sum is 16.

The square root of 21571 is about 146.8706914262. The cubic root of 21571 is about 27.8370638941.

The spelling of 21571 in words is "twenty-one thousand, five hundred seventy-one".