166693921 has 3 divisors (see below), whose sum is σ = 166706833. Its totient is φ = 166681010.

The previous prime is 166693867. The next prime is 166693927. The reversal of 166693921 is 129396661.

The square root of 166693921 is 12911.

It is a perfect power (a square), and thus also a powerful number.

166693921 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 brilliant number, because the two primes have the same length, and also an emirpimes, since its reverse is a distinct semiprime: 129396661 = 73 ⋅1772557.

It is not a de Polignac number, because 166693921 - 2⁹ = 166693409 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (166693927) by changing a digit.

It is a polite number, since it can be written in 2 ways as a sum of consecutive naturals, for example, 6456 + ... + 19366.

Almost surely, 2^166693921 is an apocalyptic number.

166693921 is the 12911-st square number.

166693921 is the 6456-th centered octagonal number.

It is an amenable number.

166693921 is a deficient number, since it is larger than the sum of its proper divisors (12912).

166693921 is an frugal number, since it uses more digits than its factorization.

166693921 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 25822 (or 12911 counting only the distinct ones).

The product of its digits is 104976, while the sum is 43.

The cubic root of 166693921 is about 550.3512037894.

Multiplying 166693921 by its product of digits (104976), we get a square (17498861050896 = 4183164²).

The spelling of 166693921 in words is "one hundred sixty-six million, six hundred ninety-three thousand, nine hundred twenty-one".