81220163 has 4 divisors (see below), whose sum is σ = 83109048. Its totient is φ = 79331280.

The previous prime is 81220159. The next prime is 81220171. The reversal of 81220163 is 36102218.

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 81220163 - 2² = 81220159 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (81220103) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 944378 + ... + 944463.

It is an arithmetic number, because the mean of its divisors is an integer number (20777262).

Almost surely, 2^81220163 is an apocalyptic number.

81220163 is a deficient number, since it is larger than the sum of its proper divisors (1888885).

81220163 is a wasteful number, since it uses less digits than its factorization.

81220163 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1888884.

The product of its (nonzero) digits is 576, while the sum is 23.

The square root of 81220163 is about 9012.2229777120. Note that the first 3 decimals coincide. The cubic root of 81220163 is about 433.0665287923.

The spelling of 81220163 in words is "eighty-one million, two hundred twenty thousand, one hundred sixty-three".