My armpits smell a little musty. What is it the deodorant I can use?

Underarm smell. Odor from underarms is mostly due to bacteria on the skin and in the follicles. Using a antibacterial soap, strong antiperspirant and topical antibiotics such as Erythromycin or Clindamycin lotions may help. Botox injected into underarms will reduce swetting and may help as well.
Antibacterial soap. Smell os form bacteria which alter sweat. An antibacterial soap such as lever 2000 which os not irritating will decrease bacteria and reduce musty smell.