21477 has 4 divisors (see below), whose sum is σ = 28640.
Its totient is φ = 14316.
The previous prime is 21467. The next prime is 21481. The reversal of 21477 is 77412.
Adding to 21477 its reverse (77412), we get a palindrome (98889).
21477 is nontrivially palindromic in base 2.
It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.
It is not a de Polignac number, because 21477 - 28 = 21221 is a prime.
It is a super-2 number, since 2×214772 = 922523058, which contains 22 as substring.
It is a D-number.
It is a Duffinian number.
It is a congruent number.
It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 21477.
It is not an unprimeable number, because it can be changed into a prime (21407) 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, 3577 + ... + 3582.
It is an arithmetic number, because the mean of its divisors is an integer number (7160).
221477 is an apocalyptic number.
It is an amenable number.
21477 is a deficient number, since it is larger than the sum of its proper divisors (7163).
21477 is an equidigital number, since it uses as much as digits as its factorization.
21477 is an odious number, because the sum of its binary digits is odd.
The sum of its prime factors is 7162.
The product of its digits is 392, while the sum is 21.
The square root of 21477 is about 146.5503326506.
The cubic root of 21477 is about 27.7965698026.
The spelling of 21477 in words is "twenty-one thousand, four hundred seventy-seven", and thus it is an iban number.