161005021 has 4 divisors (see below), whose sum is σ = 161120700. Its totient is φ = 160889344.

The previous prime is 161005007. The next prime is 161005049. The reversal of 161005021 is 120500161.

It is a happy number.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 120500161 = 1427 ⋅84443.

It can be written as a sum of positive squares in 2 ways, for example, as 87216921 + 73788100 = 9339^2 + 8590^2 .

It is a cyclic number.

It is not a de Polignac number, because 161005021 - 2⁵ = 161004989 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 161004986 and 161005004.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (161005001) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 55726 + ... + 58543.

It is an arithmetic number, because the mean of its divisors is an integer number (40280175).

Almost surely, 2^161005021 is an apocalyptic number.

It is an amenable number.

161005021 is a deficient number, since it is larger than the sum of its proper divisors (115679).

161005021 is a wasteful number, since it uses less digits than its factorization.

161005021 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 115678.

The product of its (nonzero) digits is 60, while the sum is 16.

The square root of 161005021 is about 12688.7753940244. The cubic root of 161005021 is about 544.0178377315.

Adding to 161005021 its reverse (120500161), we get a palindrome (281505182).

The spelling of 161005021 in words is "one hundred sixty-one million, five thousand, twenty-one".