1666163521 has 4 divisors (see below), whose sum is σ = 1817632944. Its totient is φ = 1514694100.

The previous prime is 1666163501. The next prime is 1666163533. The reversal of 1666163521 is 1253616661.

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: 1253616661 = 11 ⋅113965151.

It is a cyclic number.

It is not a de Polignac number, because 1666163521 - 2¹⁷ = 1666032449 is a prime.

It is a super-2 number, since 2×1666163521² = 5552201757422234882, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (1666163501) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 75734695 + ... + 75734716.

It is an arithmetic number, because the mean of its divisors is an integer number (454408236).

Almost surely, 2^1666163521 is an apocalyptic number.

1666163521 is a gapful number since it is divisible by the number (11) formed by its first and last digit.

It is an amenable number.

1666163521 is a deficient number, since it is larger than the sum of its proper divisors (151469423).

1666163521 is a wasteful number, since it uses less digits than its factorization.

1666163521 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 151469422.

The product of its digits is 38880, while the sum is 37.

The square root of 1666163521 is about 40818.6663304915. Note that the first 3 decimals coincide. The cubic root of 1666163521 is about 1185.5117804585.

The spelling of 1666163521 in words is "one billion, six hundred sixty-six million, one hundred sixty-three thousand, five hundred twenty-one".