6,100

[Math.]  78102 = 60,996,100, concatenation of 2 consecutive numbers.

 

6,105

[Math.]  A triangular number (sum of all integers from 1 to 110): 6105 = 1+2+…+109+110.

 

6,120

[Math.]  Sum (in degrees) of all internal angles of a 36-side polygon.

 

6,121

[Math.]  A sequence of prime numbers of similar pattern: 11171, 10181, 9181, 8171, 7151, 6121 and 5081, whose differences are 990, 1000, 1010, 1020, 1030 and 1040, respectively.

 

6,129

[Math.]  Each ratio, 45792/3816 = 73548/6129 = 89532/7461 = 91584/7632 = 12, uses each of 9 digits 1-9 once.

 

6,133

[Math.]  The 800th prime number.

 

6,151

[Math.]  A prime number. The 6151st prime number is 61051.

 

6,163

[Math.]  A prime number, formed by 2 consecutive odd numbers. As is 6361.

 

6,174

[Math.]  Start with a four-digit number whose digits are not all the same and form the largest and smallest four-digit numbers from those digits. Find the difference of these two numbers and repeat the procedure. Eventually, one will reach 6174 permanently. (7641–1467 = 6174).

 

6,179 

[Math.]  Two multiples of number 6179, 6179×4 = 24,716 and 6179×5 = 30,895, use each of 10 digits 0-9 once.