That's 65% more word per word

word.c

#include <stdint.h>
#include <stdio.h>

uint64_t
strtoword(char *s)
{
	uint64_t word = 0;
	word |= ((uint64_t) *(s++) & 0x1f) << 55;
	word |= ((uint64_t) *(s++) & 0x1f) << 50;
	word |= ((uint64_t) *(s++) & 0x1f) << 45;
	word |= ((uint64_t) *(s++) & 0x1f) << 40;
	word |= ((uint64_t) *(s++) & 0x1f) << 35;
	word |= ((uint64_t) *(s++) & 0x1f) << 30;
	word |= ((uint64_t) *(s++) & 0x1f) << 25;
	word |= ((uint64_t) *(s++) & 0x1f) << 20;
	word |= ((uint64_t) *(s++) & 0x1f) << 15;
	word |= ((uint64_t) *(s++) & 0x1f) << 10;
	word |= ((uint64_t) *(s++) & 0x1f) <<  5;
	word |= ((uint64_t) *(s++) & 0x1f) <<  0;
	return word;
}

void
wordtostr(uint64_t word, char *s)
{
	*(s++) = 0x60 | (word >> 55) & 0x1f;
	*(s++) = 0x60 | (word >> 50) & 0x1f;
	*(s++) = 0x60 | (word >> 45) & 0x1f;
	*(s++) = 0x60 | (word >> 40) & 0x1f;
	*(s++) = 0x60 | (word >> 35) & 0x1f;
	*(s++) = 0x60 | (word >> 30) & 0x1f;
	*(s++) = 0x60 | (word >> 25) & 0x1f;
	*(s++) = 0x60 | (word >> 20) & 0x1f;
	*(s++) = 0x60 | (word >> 15) & 0x1f;
	*(s++) = 0x60 | (word >> 10) & 0x1f;
	*(s++) = 0x60 | (word >>  5) & 0x1f;
	*(s++) = 0x60 | (word >>  0) & 0x1f;
	*s = 0;
}

int
main(void)
{
	char test[13] = "equivalences";
	char out[13];
	uint64_t word = strtoword(test);
	wordtostr(word, out);
	printf("%s => %x => %s\n", test, word, out);
}