172166721687 has 6 divisors (see below), whose sum is σ = 248685264672. Its totient is φ = 114777814452.

The previous prime is 172166721679. The next prime is 172166721767. The reversal of 172166721687 is 786127661271.

It is not a de Polignac number, because 172166721687 - 2³ = 172166721679 is a prime.

It is a super-2 number, since 2×172166721687² (a number of 23 digits) contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (172166721677) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 9564817863 + ... + 9564817880.

It is an arithmetic number, because the mean of its divisors is an integer number (41447544112).

Almost surely, 2^172166721687 is an apocalyptic number.

172166721687 is a deficient number, since it is larger than the sum of its proper divisors (76518542985).

172166721687 is a wasteful number, since it uses less digits than its factorization.

172166721687 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 19129635749 (or 19129635746 counting only the distinct ones).

The product of its digits is 2370816, while the sum is 54.

The spelling of 172166721687 in words is "one hundred seventy-two billion, one hundred sixty-six million, seven hundred twenty-one thousand, six hundred eighty-seven".