Write 1.256492751965838E-149 in decimal notation.

Step 1: The exponent for 10 is -149. Since the exponent is negative, we must move the decimal point of a number 1.2564927519658 149 places to the left.

1.2564927519658 → .----------------------------------------------------------------------------------------------------------------------------------------------------1.2564927519658

Step 2: Now we just need to replace empty spaces (dashes) with zeros and to delete old decimal point (the black one) to get:

.000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000012564927519658