from math import isqrt
from bisect import bisect_right
MAX = 10**7
temp = [True] * (MAX + 1)
temp[0:2] = [False, False]
for i in range(2, isqrt(MAX) + 1):
    if temp[i]:
        for j in range(i*i, MAX+1, i):
            temp[j] = False
primes = list(enumerate(temp))
L = [i for i, p in primes if p and list(primes[i+2])[1]]

T = int(input())
for _ in range(T):
    N = int(input())
    i = bisect_right(L, isqrt(N))
    if i >= len(L):
        i = len(L)-1
    while L[i]*(L[i]+2) > N:
        i -= 1
        if i < 0:
            break
    if i==-1:
        print(-1)
    else:
        print(L[i]*(L[i]+2))