166326721 has 6 divisors (see below), whose sum is σ = 182822066. Its totient is φ = 151206000.

The previous prime is 166326701. The next prime is 166326733. The reversal of 166326721 is 127623661.

It is a happy number.

It can be written as a sum of positive squares in only one way, i.e., 135955600 + 30371121 = 11660^2 + 5511^2 .

It is not a de Polignac number, because 166326721 - 2¹⁷ = 166195649 is a prime.

It is a super-2 number, since 2×166326721² = 55329156237223682, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (166326701) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 687180 + ... + 687421.

Almost surely, 2^166326721 is an apocalyptic number.

166326721 is a gapful number since it is divisible by the number (11) formed by its first and last digit.

It is an amenable number.

166326721 is a deficient number, since it is larger than the sum of its proper divisors (16495345).

166326721 is a wasteful number, since it uses less digits than its factorization.

166326721 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1374623 (or 1374612 counting only the distinct ones).

The product of its digits is 18144, while the sum is 34.

The square root of 166326721 is about 12896.7717278395. The cubic root of 166326721 is about 549.9467948533.

The spelling of 166326721 in words is "one hundred sixty-six million, three hundred twenty-six thousand, seven hundred twenty-one".