Numbers less than 2^-53 aren't denormals. Denormals occur when the exponent is all zeros, i.e. less than 2^-1022, the floating point representation of a double

Numbers less than 2^-53 aren't denormals. Denormals occur when the exponent is all zeros, i.e. less than 2^-1022, the floating point representation of a double (ignoring sign) is normally: 1.mantissa * 2^(exponent - 1023) A denormal occurs when the exponent is all zeros, and the representation switches to 0.mantissa * 2^(1 - 1023)