1666171581 has 32 divisors (see below), whose sum is σ = 2388009600. Its totient is φ = 1029642240.

The previous prime is 1666171523. The next prime is 1666171607. The reversal of 1666171581 is 1851716661.

It is not a de Polignac number, because 1666171581 - 2⁹ = 1666171069 is a prime.

It is a super-2 number, since 2×1666171581² = 5552255474664079122, which contains 22 as substring.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1666171511) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 1501855 + ... + 1502963.

It is an arithmetic number, because the mean of its divisors is an integer number (74625300).

Almost surely, 2^1666171581 is an apocalyptic number.

It is an amenable number.

1666171581 is a deficient number, since it is larger than the sum of its proper divisors (721838019).

1666171581 is a wasteful number, since it uses less digits than its factorization.

1666171581 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1549.

The product of its digits is 60480, while the sum is 42.

The square root of 1666171581 is about 40818.7650597124. The cubic root of 1666171581 is about 1185.5136920775.

The spelling of 1666171581 in words is "one billion, six hundred sixty-six million, one hundred seventy-one thousand, five hundred eighty-one".