161821823 has 2 divisors, whose sum is σ = 161821824. Its totient is φ = 161821822.

The previous prime is 161821819. The next prime is 161821853. The reversal of 161821823 is 328128161.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 161821823 - 2² = 161821819 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 161821823.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (161821853) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 80910911 + 80910912.

It is an arithmetic number, because the mean of its divisors is an integer number (80910912).

Almost surely, 2^161821823 is an apocalyptic number.

161821823 is a deficient number, since it is larger than the sum of its proper divisors (1).

161821823 is an equidigital number, since it uses as much as digits as its factorization.

161821823 is an evil number, because the sum of its binary digits is even.

The product of its digits is 4608, while the sum is 32.

The square root of 161821823 is about 12720.9206820890. The cubic root of 161821823 is about 544.9362470666.

Adding to 161821823 its reverse (328128161), we get a palindrome (489949984).

The spelling of 161821823 in words is "one hundred sixty-one million, eight hundred twenty-one thousand, eight hundred twenty-three".