Hadith: A man said: "O Messenger of Allah, was Adam a prophet?" He said: 'Yes.' The man said: "How long was the period between him (Adam) and Nūh?" He replied: "Ten centuries." The man asked again: "How long was the period between Nooh and Ibrahīm?" He said: "Ten centuries." The man said: "O Messenger of Allah, how many messengers were there?" He said: "Three hundred and fifteen."

عن أبي أُمامة الباهلي رضي الله عنه : أنَّ رجلا قال: يا رسول الله، أَنَبِيًّا كان آدم؟ قال: «نعم» . قال: كم بيْنه وبيْن نوح؟ قال: «عشرة قُرُون» . قال: كم بيْن نوح وإبراهيم؟ قال: «عشرة قُرُون» . قال: يا رسول الله، كم كانت الرُّسُل؟ قال: «ثلاثمائة وخمسة عشر».
[صحيح] - [رواه الطبراني والحاكم]

Abu Umāmah al-Bāhili (may Allah be pleased with him) reported: A man said: "O Messenger of Allah, was Adam a prophet?" He said: 'Yes.' The man said: "How long was the period between him (Adam) and Nūh?" He replied: "Ten centuries." The man asked again: "How long was the period between Nūh and Ibrahīm?" He said: "Ten centuries." The man said: "O Messenger of Allah, how many messengers were there?" He said: "Three hundred and fifteen."
[Authentic hadith] - [Al-Haakim - At-Tabaraani]

Explanation

Abu Umāmah (may Allah be pleased with him) mentioned in this Hadīth that a man went to the Prophet (may Allah's peace and blessings be upon him) and asked him whether Adam was a prophet. The Prophet answered in the affirmative. The man then asked about the time gap between Adam and Nūh (peace be upon them). The Prophet (may Allah's peace and blessings be upon him) said that it was ten centuries. The man further asked about the time gap between Nūh and Ibrahīm. The Prophet gave the same answer: ten centuries. The man finally asked about the number of messengers, and the Prophet (may Allah's peace and blessings be upon him) said that they were three hundred and fifteen.