166015621 has 4 divisors (see below), whose sum is σ = 166179244. Its totient is φ = 165852000.

The previous prime is 166015613. The next prime is 166015639. The reversal of 166015621 is 126510661.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 126510661 = 293 ⋅431777.

It can be written as a sum of positive squares in 2 ways, for example, as 130850721 + 35164900 = 11439^2 + 5930^2 .

It is a cyclic number.

It is not a de Polignac number, because 166015621 - 2³ = 166015613 is a prime.

It is a super-2 number, since 2×166015621² = 55122372832031282, which contains 22 as substring.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 166015621.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (166015021) 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, 80280 + ... + 82321.

It is an arithmetic number, because the mean of its divisors is an integer number (41544811).

Almost surely, 2^166015621 is an apocalyptic number.

It is an amenable number.

166015621 is a deficient number, since it is larger than the sum of its proper divisors (163623).

166015621 is a wasteful number, since it uses less digits than its factorization.

166015621 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 163622.

The product of its (nonzero) digits is 2160, while the sum is 28.

The square root of 166015621 is about 12884.7049248324. The cubic root of 166015621 is about 549.6037046057.

It can be divided in two parts, 16601 and 5621, that added together give a palindrome (22222).

The spelling of 166015621 in words is "one hundred sixty-six million, fifteen thousand, six hundred twenty-one".