odd number
integer not divisible by two
Descartes number
odd number which would have been a perfect number if one of its composite factors were prime
odd perfect number
odd number that is equal to the sum of all its divisors
titanic prime
prime number of at least 1000 decimal digits
prime number
positive integer with exactly two divisors, 1 and itself
Jevons' number
natural number
Hilbert number
positive integer of the form (4n + 1)