153

153 is a natural number that follows 152 and precedes 154. In mathematics, 153 has several notable properties. It is the 17th triangular number, since 1 + 2 + ... + 17 equals 153. It factors as 3^2 × 17, making it a composite number. The digit sum is 9, so 153 is divisible by 9 and by 3, and it is a Harshad (Niven) number in base 10. 153 is also a three-digit Armstrong (Narcissistic) number: 1^3 + 5^3 + 3^3 = 153. Thus it is the first three-digit example of this property; other three-digit Armstrong numbers are 370, 371, and 407.

In other representations, 153 has several numeral-system equivalents. In hexadecimal it is 0x99, in binary it is 10011001, and in base 9 it is 180_9 (since 1×81 + 8×9 + 0 = 153). In Roman numerals it is CLIII.

Cultural references to the number 153 appear in literature and religious texts. It is widely known in Christian tradition as the reported number of fish caught by the disciples in the Sea of Tiberias after a resurrection appearance, described in the Gospel of John. The figure has been discussed in theological and literary contexts as a symbol with various interpretations.

Overall, 153 is valued for its mixed mathematical properties, its simple digit-sum structure, and its appearances in cultural and historical contexts.