161920643 has 4 divisors (see below), whose sum is σ = 164138808. Its totient is φ = 159702480.

The previous prime is 161920613. The next prime is 161920651. The reversal of 161920643 is 346029161.

161920643 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 161920643 - 2⁶ = 161920579 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (161920613) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1108973 + ... + 1109118.

It is an arithmetic number, because the mean of its divisors is an integer number (41034702).

Almost surely, 2^161920643 is an apocalyptic number.

161920643 is a deficient number, since it is larger than the sum of its proper divisors (2218165).

161920643 is an equidigital number, since it uses as much as digits as its factorization.

161920643 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2218164.

The product of its (nonzero) digits is 7776, while the sum is 32.

The square root of 161920643 is about 12724.8042421092. The cubic root of 161920643 is about 545.0471502007.

The spelling of 161920643 in words is "one hundred sixty-one million, nine hundred twenty thousand, six hundred forty-three".