21071 has 4 divisors (see below), whose sum is σ = 22200. Its totient is φ = 19944.

The previous prime is 21067. The next prime is 21089. The reversal of 21071 is 17012.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 21071 - 2² = 21067 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21001) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 536 + ... + 573.

It is an arithmetic number, because the mean of its divisors is an integer number (5550).

2²¹⁰⁷¹ is an apocalyptic number.

21071 is a deficient number, since it is larger than the sum of its proper divisors (1129).

21071 is a wasteful number, since it uses less digits than its factorization.

21071 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1128.

The product of its (nonzero) digits is 14, while the sum is 11.

The square root of 21071 is about 145.1585340240. The cubic root of 21071 is about 27.6202994261.

Adding to 21071 its reverse (17012), we get a palindrome (38083).

The spelling of 21071 in words is "twenty-one thousand, seventy-one", and thus it is an iban number.