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 algorithm Nth root algorithm The principal "n"th root formula_1 of a positive real number "A", is the positive real solution of the equation (for integer "n" there are "n" distinct complex solutions to this equation if formula_3, but only one is positive and real). There is a very fast-converging "n"th root algorithm for finding formula_1: A special case is the familiar square-root algorithm. By setting "n" = 2, the "iteration rule" in step 2 becomes the square root iteration rule: Several different derivations of this algorithm are possible. One derivation shows it is a special case of Newton's method (also called