161936821 has 4 divisors (see below), whose sum is σ = 162014944. Its totient is φ = 161858700.

The previous prime is 161936759. The next prime is 161936833. The reversal of 161936821 is 128639161.

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.

It is a cyclic number.

It is not a de Polignac number, because 161936821 - 2¹⁵ = 161904053 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 (161936861) 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, 35865 + ... + 40126.

It is an arithmetic number, because the mean of its divisors is an integer number (40503736).

Almost surely, 2^161936821 is an apocalyptic number.

It is an amenable number.

161936821 is a deficient number, since it is larger than the sum of its proper divisors (78123).

161936821 is an equidigital number, since it uses as much as digits as its factorization.

161936821 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 78122.

The product of its digits is 15552, while the sum is 37.

The square root of 161936821 is about 12725.4399138104. The cubic root of 161936821 is about 545.0653020537.

The spelling of 161936821 in words is "one hundred sixty-one million, nine hundred thirty-six thousand, eight hundred twenty-one".