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 number is a positive integer if and only if the number is itself a positive integer. The digital root of formula_1 is formula_1 itself if and only if the number has exactly one digit. The digital root of formula_1 is less than formula_1 if and only if the number is greater than or equal to 10. The digital root of formula_45 + formula_46 is digital root of the sum of the digital root of formula_45 and the digital root of formula_46. The digital root of formula_45 - formula_46 is congruent with the difference of the digital root of formula_45 and