72171581 has 4 divisors (see below), whose sum is σ = 72326592. Its totient is φ = 72016572.

The previous prime is 72171563. The next prime is 72171611. The reversal of 72171581 is 18517127.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4, and also an emirpimes, since its reverse is a distinct semiprime: 18517127 = 167 ⋅110881.

It is a cyclic number.

It is not a de Polignac number, because 72171581 - 2¹⁰ = 72170557 is a prime.

It is a super-2 number, since 2×72171581² = 10417474208079122, which contains 22 as substring.

It is a Duffinian number.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (72171181) by changing a digit.

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, 76805 + ... + 77738.

It is an arithmetic number, because the mean of its divisors is an integer number (18081648).

Almost surely, 2^72171581 is an apocalyptic number.

It is an amenable number.

72171581 is a deficient number, since it is larger than the sum of its proper divisors (155011).

72171581 is a wasteful number, since it uses less digits than its factorization.

72171581 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 155010.

The product of its digits is 3920, while the sum is 32.

The square root of 72171581 is about 8495.3858652800. The cubic root of 72171581 is about 416.3469680632.

The spelling of 72171581 in words is "seventy-two million, one hundred seventy-one thousand, five hundred eighty-one".