Radical of an integer ($\mathrm{rad}(n)={\prod }_{p\mid n}p$)

The radical of a positive integer is the product of its distinct prime factors, with $\mathrm{rad}(1)=1$. It is the squarefree integer recording which primes occur, independently of their exponents. Equality of radicals is equivalent to mutual divisibility by sufficiently high positive powers.