I am just starting out on a journey to understand microcontroller and microprocessor design. Have read briefly on their differences (ARM7 and Intel i3, i5 & i7). Couldn't find any information on their differences in architecture. for example, ARM7 has 21 external interrupt pins. but couldnt find definite information about intel's external interrupt pins. or how On-chip static ram is 8 kb-40 kb, on-chip flash memory is 32 kb-512 kb, the wide interface is 128 bit, or accelerator allows 60 MHz high-speed operation for ARM7. couldn't find any corresponding information on intel's processors.
ARM7 has 21 external interrupt pins
No, a generic ARM7 has two external interrupts: IRQ and FIQ.
The problem here is "architecture" versus "implementation". ARM7 is an architecture. LPC2148 (for example) is an implementation of that architecture. The implementation has pins, cache, etc. You got that information from this page, perhaps?
Intel handle interrupts very differently. A datasheet for Intel. It has no external interrupt pins - instead it has a PCI-E bus, and messages on that bus can be translated into interrupts.
As @pjc50 noted, you are confusing architecture vs implementation. Also, the ARM implementation you noted is a microcontroller or SOC (system on chip). This is why it has RAM, FLASH, interrupt controller, etc. on chip.
On the other hand, the Intel chips mentioned are microprocessors. All that is on-chip is basically the CPU, cache memory and maybe on-board graphics. Everything else, interrupt controller, RAM, non-volatile storage, etc, is off-chip, in the “chipset”, DDR RAM modules and external storage.