81558194 has 4 divisors (see below), whose sum is σ = 122337294. Its totient is φ = 40779096.

The previous prime is 81558193. The next prime is 81558199. The reversal of 81558194 is 49185518.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 49185518 = 2 ⋅24592759.

It can be written as a sum of positive squares in only one way, i.e., 79834225 + 1723969 = 8935^2 + 1313^2 .

It is not an unprimeable number, because it can be changed into a prime (81558193) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 20389547 + ... + 20389550.

Almost surely, 2^81558194 is an apocalyptic number.

81558194 is a deficient number, since it is larger than the sum of its proper divisors (40779100).

81558194 is a wasteful number, since it uses less digits than its factorization.

81558194 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 40779099.

The product of its digits is 57600, while the sum is 41.

The square root of 81558194 is about 9030.9575350568. The cubic root of 81558194 is about 433.6664918535. Note that the first 3 decimals are identical.

The spelling of 81558194 in words is "eighty-one million, five hundred fifty-eight thousand, one hundred ninety-four".