21473 has 4 divisors (see below), whose sum is σ = 21780. Its totient is φ = 21168.

The previous prime is 21467. The next prime is 21481. The reversal of 21473 is 37412.

It is a happy number.

21473 is nontrivially palindromic in base 11.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length.

It can be written as a sum of positive squares in 2 ways, for example, as 18769 + 2704 = 137^2 + 52^2 .

It is a cyclic number.

It is not a de Polignac number, because 21473 - 2¹² = 17377 is a prime.

It is a super-2 number, since 2×21473² = 922179458, which contains 22 as substring.

It is a Duffinian number.

21473 is an undulating number in base 11 and base 14.

It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 21473.

It is not an unprimeable number, because it can be changed into a prime (21433) 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, 11 + ... + 207.

It is an arithmetic number, because the mean of its divisors is an integer number (5445).

2²¹⁴⁷³ is an apocalyptic number.

It is an amenable number.

21473 is a deficient number, since it is larger than the sum of its proper divisors (307).

21473 is a wasteful number, since it uses less digits than its factorization.

21473 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 306.

The product of its digits is 168, while the sum is 17.

The square root of 21473 is about 146.5366848267. The cubic root of 21473 is about 27.7948440311.

Adding to 21473 its reverse (37412), we get a palindrome (58885).

It can be divided in two parts, 2147 and 3, that multiplied together give a triangular number (6441 = T₁₁₃).

The spelling of 21473 in words is "twenty-one thousand, four hundred seventy-three", and thus it is an iban number.