166610021 has 4 divisors (see below), whose sum is σ = 168167232. Its totient is φ = 165052812.

The previous prime is 166610011. The next prime is 166610029. The reversal of 166610021 is 120016661.

166610021 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

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.

It is a cyclic number.

It is not a de Polignac number, because 166610021 - 2¹⁰ = 166608997 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (166610029) 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, 778445 + ... + 778658.

It is an arithmetic number, because the mean of its divisors is an integer number (42041808).

Almost surely, 2^166610021 is an apocalyptic number.

It is an amenable number.

166610021 is a deficient number, since it is larger than the sum of its proper divisors (1557211).

166610021 is a wasteful number, since it uses less digits than its factorization.

166610021 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1557210.

The product of its (nonzero) digits is 432, while the sum is 23.

The square root of 166610021 is about 12907.7504236796. The cubic root of 166610021 is about 550.2588544610.

Adding to 166610021 its reverse (120016661), we get a palindrome (286626682).

The spelling of 166610021 in words is "one hundred sixty-six million, six hundred ten thousand, twenty-one".