[1] Other than 1 and the number itself, 58 can be formed by multiplying two primes 2 and 29, making it a semiprime.
[2] 58 is not divisible by any square number other than 1, making it a square-free integer[3] A semiprime that is not square numbers is called a squarefree semiprime, and 58 is among them.
[4] 58 is equal to the sum of the first seven consecutive prime numbers:[5] This is a difference of 1 from the seventeenth prime number and seventh super-prime, 59.
, making fifty-eight the sixth noncototient;[10] however, the totient summatory function over the first thirteen integers is 58.
[14] 58 represents twice the sum between the first two discrete biprimes 14 + 15 = 29, with the first two members of the first such triplet 33 and 34 (or twice 17, the fourth super-prime) respectively the twenty-first and twenty-second composite numbers,[15] and 22 itself the thirteenth composite.
The first triplet is the only triplet in the sequence of consecutive discrete biprimes whose members collectively have prime factorizations that nearly span a set of consecutive prime numbers.
[16] The fifth repdigit is the product between the thirteenth and fifty-eighth primes, 58 is also the smallest integer in decimal whose square root has a simple continued fraction with period 7.