21268 has 12 divisors (see below), whose sum is σ = 40180. Its totient is φ = 9792.

The previous prime is 21247. The next prime is 21269. The reversal of 21268 is 86212.

It is a happy number.

It can be written as a sum of positive squares in 2 ways, for example, as 11664 + 9604 = 108^2 + 98^2 .

It is a hoax number, since the sum of its digits (19) coincides with the sum of the digits of its distinct prime factors.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21269) by changing a digit.

21268 is an untouchable number, because it is not equal to the sum of proper divisors of any number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 153 + ... + 256.

2²¹²⁶⁸ is an apocalyptic number.

It is an amenable number.

21268 is a deficient number, since it is larger than the sum of its proper divisors (18912).

21268 is a wasteful number, since it uses less digits than its factorization.

21268 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 426 (or 424 counting only the distinct ones).

The product of its digits is 192, while the sum is 19.

The square root of 21268 is about 145.8355237931. The cubic root of 21268 is about 27.7061097706.

It can be divided in two parts, 21 and 268, that added together give a square (289 = 17²).

The spelling of 21268 in words is "twenty-one thousand, two hundred sixty-eight".