172720557917 has 2 divisors, whose sum is σ = 172720557918. Its totient is φ = 172720557916.

The previous prime is 172720557859. The next prime is 172720557929. The reversal of 172720557917 is 719755027271.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 151734399961 + 20986157956 = 389531^2 + 144866^2 .

It is a cyclic number.

It is not a de Polignac number, because 172720557917 - 2¹² = 172720553821 is a prime.

It is a super-2 number, since 2×172720557917² (a number of 23 digits) contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (172720557967) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 86360278958 + 86360278959.

It is an arithmetic number, because the mean of its divisors is an integer number (86360278959).

Almost surely, 2^172720557917 is an apocalyptic number.

It is an amenable number.

172720557917 is a deficient number, since it is larger than the sum of its proper divisors (1).

172720557917 is an equidigital number, since it uses as much as digits as its factorization.

172720557917 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 2160900, while the sum is 53.

The spelling of 172720557917 in words is "one hundred seventy-two billion, seven hundred twenty million, five hundred fifty-seven thousand, nine hundred seventeen".