21069 has 6 divisors (see below), whose sum is σ = 30446. Its totient is φ = 14040.

The previous prime is 21067. The next prime is 21089. The reversal of 21069 is 96012.

21069 is nontrivially palindromic in base 8.

It can be written as a sum of positive squares in only one way, i.e., 19044 + 2025 = 138^2 + 45^2 .

It is not a de Polignac number, because 21069 - 2¹ = 21067 is a prime.

It is a super-2 number, since 2×21069² = 887805522, which contains 22 as substring.

It is a Duffinian number.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21061) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 1162 + ... + 1179.

2²¹⁰⁶⁹ is an apocalyptic number.

It is an amenable number.

21069 is a deficient number, since it is larger than the sum of its proper divisors (9377).

21069 is a wasteful number, since it uses less digits than its factorization.

21069 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2347 (or 2344 counting only the distinct ones).

The product of its (nonzero) digits is 108, while the sum is 18.

The square root of 21069 is about 145.1516448408. The cubic root of 21069 is about 27.6194255181.

The spelling of 21069 in words is "twenty-one thousand, sixty-nine".