166240821 has 4 divisors (see below), whose sum is σ = 221654432. Its totient is φ = 110827212.

The previous prime is 166240813. The next prime is 166240829. The reversal of 166240821 is 128042661.

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: 128042661 = 3 ⋅42680887.

It is an interprime number because it is at equal distance from previous prime (166240813) and next prime (166240829).

It is not a de Polignac number, because 166240821 - 2³ = 166240813 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 (166240829) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 27706801 + ... + 27706806.

It is an arithmetic number, because the mean of its divisors is an integer number (55413608).

Almost surely, 2^166240821 is an apocalyptic number.

It is an amenable number.

166240821 is a deficient number, since it is larger than the sum of its proper divisors (55413611).

166240821 is an equidigital number, since it uses as much as digits as its factorization.

166240821 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 55413610.

The product of its (nonzero) digits is 4608, while the sum is 30.

The square root of 166240821 is about 12893.4410069616. The cubic root of 166240821 is about 549.8521045870.

The spelling of 166240821 in words is "one hundred sixty-six million, two hundred forty thousand, eight hundred twenty-one".