Using a potential energy curve (based primarily on the RKR potential of Amiot and Verges [J. Chem. Phys. 112, 7068 (2000)]) and a dipole moment function (based primarily on ab initio calculations of Park [Chem. Phys. 257, 135 (2000)]), we have calculated radiative transition probabilities (Einstein A coefficients), radiative lifetimes, and dipole moment expectation values involving all vibrational levels (for several rotational quantum numbers) of the X (1)Sigma(+) ground state of (KRb)-K-39-Rb-85. We observe that the radiative lifetimes of vibrationally excited levels, in particular, are similar to10(3)-10(6) seconds, far too long to be significant in most ultracold experiments involving (KRb)-K-39-Rb-85 or its isotopomers. Comparison with other molecules (LiH and HF) suggests that simple scaling (Asimilar tomu(2)nu(3)similar totau(-1)) will predict similarly long lifetimes for many other heteronuclear molecules, e.g., RbCs. (C) 2004 American Institute of Physics.