21427 has 4 divisors (see below), whose sum is σ = 24496. Its totient is φ = 18360.

The previous prime is 21419. The next prime is 21433. The reversal of 21427 is 72412.

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 21427 - 2³ = 21419 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21427.

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, 1524 + ... + 1537.

It is an arithmetic number, because the mean of its divisors is an integer number (6124).

2²¹⁴²⁷ is an apocalyptic number.

21427 is a deficient number, since it is larger than the sum of its proper divisors (3069).

21427 is an equidigital number, since it uses as much as digits as its factorization.

21427 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3068.

The product of its digits is 112, while the sum is 16.

The square root of 21427 is about 146.3796433935. The cubic root of 21427 is about 27.7749822372.

Adding to 21427 its reverse (72412), we get a palindrome (93839).

It can be divided in two parts, 214 and 27, that multiplied together give a triangular number (5778 = T₁₀₇).

The spelling of 21427 in words is "twenty-one thousand, four hundred twenty-seven", and thus it is an iban number.