21418 has 4 divisors (see below), whose sum is σ = 32130. Its totient is φ = 10708.

The previous prime is 21407. The next prime is 21419. The reversal of 21418 is 81412.

It is a happy number.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in only one way, i.e., 12769 + 8649 = 113^2 + 93^2 .

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

It is a nialpdrome in base 13.

It is not an unprimeable number, because it can be changed into a prime (21419) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 5353 + ... + 5356.

2²¹⁴¹⁸ is an apocalyptic number.

21418 is a deficient number, since it is larger than the sum of its proper divisors (10712).

21418 is a wasteful number, since it uses less digits than its factorization.

21418 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 10711.

The product of its digits is 64, while the sum is 16.

The square root of 21418 is about 146.3488981851. The cubic root of 21418 is about 27.7710929099.

It can be divided in two parts, 214 and 18, that added together give a palindrome (232).

The spelling of 21418 in words is "twenty-one thousand, four hundred eighteen".