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
Digital root the digital root of formula_46 modulo 9. Especially, we can define the digital root of minus formula_1 as follows: The digital root of formula_45 × formula_46 is digital root of the product of the digital root of formula_45 and the digital root of formula_46. This article is about the digital root in decimal or base ten, hence it is the number mod 9. It is nothing different as the number converted to base 9 and then only the last digit taken. In other radixes the digital root is number mod (base-1) so in base 12 a digital root of a