72171805 has 4 divisors (see below), whose sum is σ = 86606172. Its totient is φ = 57737440.

The previous prime is 72171773. The next prime is 72171829. The reversal of 72171805 is 50817127.

It is a happy number.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 50817127 = 131 ⋅387917.

It can be written as a sum of positive squares in 2 ways, for example, as 38601369 + 33570436 = 6213^2 + 5794^2 .

It is not a de Polignac number, because 72171805 - 2⁵ = 72171773 is a prime.

It is a Smith number, since the sum of its digits (31) 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 an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 7217176 + ... + 7217185.

It is an arithmetic number, because the mean of its divisors is an integer number (21651543).

Almost surely, 2^72171805 is an apocalyptic number.

It is an amenable number.

72171805 is a deficient number, since it is larger than the sum of its proper divisors (14434367).

72171805 is a wasteful number, since it uses less digits than its factorization.

72171805 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 14434366.

The product of its (nonzero) digits is 3920, while the sum is 31.

The square root of 72171805 is about 8495.3990488970. The cubic root of 72171805 is about 416.3473988035.

The spelling of 72171805 in words is "seventy-two million, one hundred seventy-one thousand, eight hundred five".