21270 has 16 divisors (see below), whose sum is σ = 51120. Its totient is φ = 5664.

The previous prime is 21269. The next prime is 21277. The reversal of 21270 is 7212.

It is an alternating number because its digits alternate between even and odd.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21277) 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 7 ways as a sum of consecutive naturals, for example, 325 + ... + 384.

It is an arithmetic number, because the mean of its divisors is an integer number (3195).

2²¹²⁷⁰ is an apocalyptic number.

21270 is an abundant number, since it is smaller than the sum of its proper divisors (29850).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

It is a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (25560).

21270 is a wasteful number, since it uses less digits than its factorization.

21270 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 719.

The product of its (nonzero) digits is 28, while the sum is 12.

The square root of 21270 is about 145.8423806717. The cubic root of 21270 is about 27.7069782190.

Adding to 21270 its reverse (7212), we get a palindrome (28482).

It can be divided in two parts, 212 and 70, that added together give a palindrome (282).

The spelling of 21270 in words is "twenty-one thousand, two hundred seventy", and thus it is an iban number.