170 is the natural number following 169 and preceding 171 .

Ordinal	One hundred [and] seventy
Cardinal	170th
Factorization
Roman numeral	CLXX
Binary	10101010
Hexadecimal	A0

One hundred seventy a sphenic number. It is the smallest n for which φ(n) and σ(n) are both square. But 170 is never a solution for φ(x), making it a nontotient. Nor is it ever a solution to x - φ(x), making it a noncototient.

One hundred seventy is also

• The designation of spur route of Interstate 70.
• The year AD 170 or 170 BC.

Numbers in the 170s

171 = 3^2 19, triangular number, Harshad number

172 = 2^2 43, noncototient

173 = prime number, Sophie Germain prime, sum of three consecutive primes (53 + 59 + 61)

174 = 2 3 29, sphenic number, nontotient

175 = 5^2 7

176 = 2^4 11, pentagonal number, octagonal number, octagonal pentagonal number , self number

177 = 3 59

178 = 2 89

179 = prime number, Sophie Germain prime, safe prime, strictly non-palindromic number