172137991 has 4 divisors (see below), whose sum is σ = 172168992. Its totient is φ = 172106992.

The previous prime is 172137989. The next prime is 172138007. The reversal of 172137991 is 199731271.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 172137991 - 2¹ = 172137989 is a prime.

It is a Smith number, since the sum of its digits (40) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (172137961) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 4630 + ... + 19123.

It is an arithmetic number, because the mean of its divisors is an integer number (43042248).

Almost surely, 2^172137991 is an apocalyptic number.

172137991 is a deficient number, since it is larger than the sum of its proper divisors (31001).

172137991 is an equidigital number, since it uses as much as digits as its factorization.

172137991 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 31000.

The product of its digits is 23814, while the sum is 40.

The square root of 172137991 is about 13120.1368514204. The cubic root of 172137991 is about 556.2784595800.

The spelling of 172137991 in words is "one hundred seventy-two million, one hundred thirty-seven thousand, nine hundred ninety-one".