166821 has 8 divisors (see below), whose sum is σ = 235584. Its totient is φ = 104640.

The previous prime is 166807. The next prime is 166823. The reversal of 166821 is 128661.

166821 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 166821 - 2⁷ = 166693 is a prime.

It is a Smith number, since the sum of its digits (24) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a plaindrome in base 15.

It is a junction number, because it is equal to n+sod(n) for n = 166791 and 166800.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (166823) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 1585 + ... + 1686.

It is an arithmetic number, because the mean of its divisors is an integer number (29448).

2¹⁶⁶⁸²¹ is an apocalyptic number.

It is an amenable number.

166821 is a deficient number, since it is larger than the sum of its proper divisors (68763).

166821 is a wasteful number, since it uses less digits than its factorization.

166821 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3291.

The product of its digits is 576, while the sum is 24.

The square root of 166821 is about 408.4372656847. The cubic root of 166821 is about 55.0491021557.

The spelling of 166821 in words is "one hundred sixty-six thousand, eight hundred twenty-one".