1166172021 has 18 divisors (see below), whose sum is σ = 1959487062. Its totient is φ = 666383760.

The previous prime is 1166171977. The next prime is 1166172079. The reversal of 1166172021 is 1202716611.

It is a happy number.

1166172021 is a `hidden beast` number, since 1 + 1 + 6 + 617 + 20 + 21 = 666.

It can be written as a sum of positive squares in only one way, i.e., 1114892100 + 51279921 = 33390^2 + 7161^2 .

It is not a de Polignac number, because 1166172021 - 2⁹ = 1166171509 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1166172421) by changing a digit.

It is a polite number, since it can be written in 17 ways as a sum of consecutive naturals, for example, 1321750 + ... + 1322631.

Almost surely, 2^1166172021 is an apocalyptic number.

It is an amenable number.

1166172021 is a deficient number, since it is larger than the sum of its proper divisors (793315041).

1166172021 is a wasteful number, since it uses less digits than its factorization.

1166172021 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2644401 (or 2644391 counting only the distinct ones).

The product of its (nonzero) digits is 1008, while the sum is 27.

The square root of 1166172021 is about 34149.2609144034. The cubic root of 1166172021 is about 1052.5777995348.

Adding to 1166172021 its reverse (1202716611), we get a palindrome (2368888632).

The spelling of 1166172021 in words is "one billion, one hundred sixty-six million, one hundred seventy-two thousand, twenty-one".