161818021 has 8 divisors (see below), whose sum is σ = 167290200. Its totient is φ = 156418560.

The previous prime is 161818001. The next prime is 161818031. The reversal of 161818021 is 120818161.

It can be written as a sum of positive squares in 4 ways, for example, as 172225 + 161645796 = 415^2 + 12714^2 .

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

It is a cyclic number.

It is not a de Polignac number, because 161818021 - 2⁵ = 161817989 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 (161818001) 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 7 ways as a sum of consecutive naturals, for example, 13636 + ... + 22573.

It is an arithmetic number, because the mean of its divisors is an integer number (20911275).

Almost surely, 2^161818021 is an apocalyptic number.

It is an amenable number.

161818021 is a deficient number, since it is larger than the sum of its proper divisors (5472179).

161818021 is a wasteful number, since it uses less digits than its factorization.

161818021 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 36359.

The product of its (nonzero) digits is 768, while the sum is 28.

The square root of 161818021 is about 12720.7712423422. The cubic root of 161818021 is about 544.9319792784.

The spelling of 161818021 in words is "one hundred sixty-one million, eight hundred eighteen thousand, twenty-one".