161956217 has 4 divisors (see below), whose sum is σ = 163192656. Its totient is φ = 160719780.

The previous prime is 161956211. The next prime is 161956231. The reversal of 161956217 is 712659161.

161956217 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, and also a Blum integer, because the two primes are equal to 3 mod 4, and also an emirpimes, since its reverse is a distinct semiprime: 712659161 = 1031 ⋅691231.

It is a cyclic number.

It is not a de Polignac number, because 161956217 - 2⁶ = 161956153 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (161956211) 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, 618023 + ... + 618284.

It is an arithmetic number, because the mean of its divisors is an integer number (40798164).

Almost surely, 2^161956217 is an apocalyptic number.

It is an amenable number.

161956217 is a deficient number, since it is larger than the sum of its proper divisors (1236439).

161956217 is a wasteful number, since it uses less digits than its factorization.

161956217 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1236438.

The product of its digits is 22680, while the sum is 38.

The square root of 161956217 is about 12726.2019864530. The cubic root of 161956217 is about 545.0870629365.

The spelling of 161956217 in words is "one hundred sixty-one million, nine hundred fifty-six thousand, two hundred seventeen".