166610621 has 4 divisors (see below), whose sum is σ = 166800192. Its totient is φ = 166421052.

The previous prime is 166610599. The next prime is 166610627. The reversal of 166610621 is 126016661.

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: 126016661 = 2473 ⋅50957.

It is a cyclic number.

It is not a de Polignac number, because 166610621 - 2²⁶ = 99501757 is a prime.

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 (166610627) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 93461 + ... + 95226.

It is an arithmetic number, because the mean of its divisors is an integer number (41700048).

Almost surely, 2^166610621 is an apocalyptic number.

It is an amenable number.

166610621 is a deficient number, since it is larger than the sum of its proper divisors (189571).

166610621 is an equidigital number, since it uses as much as digits as its factorization.

166610621 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 189570.

The product of its (nonzero) digits is 2592, while the sum is 29.

The square root of 166610621 is about 12907.7736655087. The cubic root of 166610621 is about 550.2595149953.

The spelling of 166610621 in words is "one hundred sixty-six million, six hundred ten thousand, six hundred twenty-one".