# 9890881

This number is a composite.

Single Curio View: (Seek other curios for this number)

The smallest base-2 pseudoprime q such that 2q+1 is also a
base-2 pseudoprime — a “Sophie Germain pseudoprime,” so to
speak. Using Feitsma’s
table, one can find two more such numbers < 2^64:
23456248059221 = R23 and 96076792050570581 = R29, where Rn
= (4^n-1)/3 is a repunit in radix 4, which often yields a
large Sophie Germain pseudoprime; 9890881 (a Carmichael
number) is not of the same type. Can we find a
“pseudo-Cunningham chain” of length 3? [Yosei]
Submitted: 2019-07-22 08:13:27; Last Modified: 2019-07-22 09:05:27.

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