920 is the third-largest idoneal number (the largest is 10X0, and the second-largest is 959).
920 is the largest idoneal number n such that n+1 is prime (although n−1 is also prime for n=920, but n−1 is also prime for n=the largest idoneal number (10X0)).
Let f(n) be the smallest multiple of n which is not Harshad number, 920 is the n<=1000 such that f(n) is largest (2EXEEEEX0).
Let f(n) be the smallest Euler-Jacobi pseudoprime to base n (not necessarily exceeding n), 920 is the n<=4000 such that f(n) is largest (2455, note that 2455 = 2^10+1, and 10 is the base of the numeral system of this wiki), and all other n<=4000 have f(n) <= 1940 (the second-largest f(n) for n<=4000 is f(16E6) = 1925, and the third-largest f(n) for n<=4000 is f(1870) = 1871).
Let f(n) be the smallest strong pseudoprime to base n (not necessarily exceeding n), 920 is the n<=2800 such that f(n) is largest (2455, note that 2455 = 2^10+1, and 10 is the base of the numeral system of this wiki), and all other n<=2800 have f(n) <= 1940 (the second-largest f(n) for n<=2800 is f(16E6) = 1925, and the third-largest f(n) for n<=2800 is f(1870) = 1871). (note that f(2888) = 2887, which is greater than f(920) = 2455)
There are no known generalized Wieferich primes to base 920, and they are conjectured not to exist.
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