The odd natural number which is mentioned as X is 175.
Step-by-step explanation:
- By prime Factorization method .
- Step 1  : The prime factor for 40 is = 2×2×2×5.
- Step 2 :The prime factor for 1400 is = 2×2×2×5×5×7.
- Step 3 : the prime factor for the unknown  natural odd number is to be find by comparing the factors of 40 and 1400. 
- Step 4 : Lcm is known as least common multiple. 
- Step 5 : Thus we can see  the 5×5×7 in 1400 as different factors from the factors of 40. 
- Step 6 : So lets multiply the factors we get number 175 which satisfies the condition of the odd number. 
- Step 7 :  The prime factors of 175 are 5×5×7.