172638209 has 4 divisors (see below), whose sum is σ = 172664916. Its totient is φ = 172611504.

The previous prime is 172638157. The next prime is 172638217. The reversal of 172638209 is 902836271.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length, and also an emirpimes, since its reverse is a distinct semiprime: 902836271 = 22963 ⋅39317.

It can be written as a sum of positive squares in 2 ways, for example, as 53217025 + 119421184 = 7295^2 + 10928^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-172638209 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (172638239) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 3107 + ... + 18839.

It is an arithmetic number, because the mean of its divisors is an integer number (43166229).

It is a Proth number, since it is equal to 10537 ⋅ 2¹⁴ + 1 and 10537 < 2¹⁴.

Almost surely, 2^172638209 is an apocalyptic number.

It is an amenable number.

172638209 is a deficient number, since it is larger than the sum of its proper divisors (26707).

172638209 is a wasteful number, since it uses less digits than its factorization.

172638209 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 26706.

The product of its (nonzero) digits is 36288, while the sum is 38.

The square root of 172638209 is about 13139.1860097953. The cubic root of 172638209 is about 556.8167707290.

The spelling of 172638209 in words is "one hundred seventy-two million, six hundred thirty-eight thousand, two hundred nine".