400 (number)
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| Cardinal | four hundred | |||
| Ordinal | 400th (four hundredth) |
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| Factorization | 24× 52 | |||
| Divisors | 1, 2, 4, 5, 8, 10, 16, 20, 25, 40, 50, 80, 100, 200, 400 | |||
| Roman numeral | CD | |||
| Binary | 1100100002 | |||
| Ternary | 1122113 | |||
| Quaternary | 121004 | |||
| Quinary | 31005 | |||
| Senary | 15046 | |||
| Octal | 6208 | |||
| Duodecimal | 29412 | |||
| Hexadecimal | 19016 | |||
| Vigesimal | 10020 | |||
| Base 36 | B436 | |||
| Hebrew | ת (Tav) | |||
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 400 grads, which is equal to 360 degrees and 2π radians. (Degrees and radians are the SI accepted units).
400 is a self number in base 10, since there is no integer that added to the sum of its own digits results in 400. On the other hand, 400 is divisible by the sum of its own base 10 digits, making it a Harshad number.
Four hundred is also
A prime number, tetranacci number, sum of seven consecutive primes (43 + 47 + 53 + 59 + 61 + 67 + 71), sum of nine consecutive primes (29 + 31 + 37 + 41 + 43 + 47 + 53 + 59 + 61), Chen prime,Eisenstein prime with no imaginary part, Mertens function returns 0, member of the Mian–Chowla sequence.
402 = 2 × 3 × 67, sphenic number, nontotient, Harshad number,
403 = 13 × 31, Mertens function returns 0.
404 = 22 × 101, Mertens function returns 0, nontotient, noncototient.
405 = 34 × 5, Mertens function returns 0,Harshad number;
406 = 2 × 7 × 29, sphenic number, triangular number, centered nonagonal number, nontotient
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Wikipedia