Your answer depends on the anticipated rate of return at which it would be invested as well as the rate of compunding (i.e. annually, monthly, daily). You also appear to be asking a second question which is what would $1,000,000 received 20 years from now be worth, the answer to which depends on the discount rate used (i.e. inflation or some other rate).
For example, $1MM invested today at 5% compunded annually at the end of the year would be worth $2,653,297.71. Alternatively, it would take an investment of $376,889.48 invested at 5% compounded annually to generate $1,000,000 20 years from now.
Do you have specific assumptions regarding discount rates and compunding periods?