172991506 has 4 divisors (see below), whose sum is σ = 259487262. Its totient is φ = 86495752.

The previous prime is 172991503. The next prime is 172991509. The reversal of 172991506 is 605199271.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 605199271 = 647 ⋅935393.

It is an interprime number because it is at equal distance from previous prime (172991503) and next prime (172991509).

It can be written as a sum of positive squares in only one way, i.e., 147841281 + 25150225 = 12159^2 + 5015^2 .

It is a super-2 number, since 2×172991506² = 59852122296296072, which contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (172991503) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 43247875 + ... + 43247878.

Almost surely, 2^172991506 is an apocalyptic number.

172991506 is a deficient number, since it is larger than the sum of its proper divisors (86495756).

172991506 is an equidigital number, since it uses as much as digits as its factorization.

172991506 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 86495755.

The product of its (nonzero) digits is 34020, while the sum is 40.

The square root of 172991506 is about 13152.6235405717. The cubic root of 172991506 is about 557.1963461310.

The spelling of 172991506 in words is "one hundred seventy-two million, nine hundred ninety-one thousand, five hundred six".