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170 is the natural number following 169 and preceding 171.
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
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
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