400 (number) third perfect number, a number whose divisors add up to the actual number (1+2+4+8+16+31+62+124+248=496). 497 = 7 × 71, sum of five consecutive primes (89 + 97 + 101 + 103 + 107) 498 = 2 × 3 × 83, sphenic number, untouchable number, admirable number, abundant number A prime number, Chen prime 400 (number) 400 (four hundred) is the natural number following 399 and preceding 401. 400 is the square of 20. 400 is the sum of the powers of 7 from 0 to 3, thus making it a repdigit in base 7 (1111). A circle is divided into
Nth root and 1, "ω", "ω", ... "ω" are the "n"th roots of unity. For example, the four different fourth roots of 2 are In polar form, a single "n"th root may be found by the formula Here "r" is the magnitude (the modulus, also called the absolute value) of the number whose root is to be taken; if the number can be written as "a+bi" then formula_97. Also, formula_98 is the angle formed as one pivots on the origin counterclockwise from the positive horizontal axis to a ray going from the origin to the number; it has the properties that formula_99