21458 has 4 divisors (see below), whose sum is σ = 32190. Its totient is φ = 10728.

The previous prime is 21433. The next prime is 21467. The reversal of 21458 is 85412.

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., 16129 + 5329 = 127^2 + 73^2 .

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

It is an unprimeable number.

21458 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 as a sum of consecutive naturals, namely, 5363 + ... + 5366.

2²¹⁴⁵⁸ is an apocalyptic number.

21458 is a deficient number, since it is larger than the sum of its proper divisors (10732).

21458 is a wasteful number, since it uses less digits than its factorization.

21458 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 10731.

The product of its digits is 320, while the sum is 20.

The square root of 21458 is about 146.4854941624. The cubic root of 21458 is about 27.7883704786.

It can be divided in two parts, 214 and 58, that added together give a palindrome (272).

The spelling of 21458 in words is "twenty-one thousand, four hundred fifty-eight".