Canto 3 -
Araṇya-kāṇḍa
Chapter 55: Rāvaṇa Flatters Sītā
Text 3.55.14

दश राक्षसकोट्यश्च द्वाविंशतिरथापराः।
तेषां प्रभुरहं सीते सर्वेषां भीमकर्मणाम्॥

daśa rākṣasa-koṭyaś ca dvā-viṁśatir athāparāḥ
teṣāṁ prabhur ahaṁ sīte sarveṣāṁ bhīma-karmaṇām

daśa = there are ten; rākṣasa-koṭyaḥ = crores of rākṣasas; ca = and; dvā-viṁśatiḥ = twenty-two [crores of them]; atha aparāḥ = another; teṣām = of them; prabhuḥ = am the [only] lord; aham = [but] I; sīte = Sītā; sarveṣām = of all; bhīma-karmaṇām = of them whose deeds are terrible.

Sītā, there are ten crores of rākṣasas and another twenty-two [crores of them, but] I am the [only] lord of all of them whose deeds are terrible.

There were 320,000,000 rākṣasas.