161821243 has 4 divisors (see below), whose sum is σ = 164874528. Its totient is φ = 158767960.

The previous prime is 161821237. The next prime is 161821267. The reversal of 161821243 is 342128161.

161821243 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 an emirpimes, since its reverse is a distinct semiprime: 342128161 = 223 ⋅1534207.

It is a cyclic number.

It is not a de Polignac number, because 161821243 - 2⁹ = 161820731 is a prime.

It is a super-2 number, since 2×161821243² = 52372229372130098, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (161821223) 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, 1526563 + ... + 1526668.

It is an arithmetic number, because the mean of its divisors is an integer number (41218632).

Almost surely, 2^161821243 is an apocalyptic number.

161821243 is a deficient number, since it is larger than the sum of its proper divisors (3053285).

161821243 is an equidigital number, since it uses as much as digits as its factorization.

161821243 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3053284.

The product of its digits is 2304, while the sum is 28.

The square root of 161821243 is about 12720.8978849765. The cubic root of 161821243 is about 544.9355960144.

The spelling of 161821243 in words is "one hundred sixty-one million, eight hundred twenty-one thousand, two hundred forty-three".