81531158 has 4 divisors (see below), whose sum is σ = 122296740. Its totient is φ = 40765578.

The previous prime is 81531143. The next prime is 81531169. The reversal of 81531158 is 85113518.

It is a happy number.

It is a semiprime because it is the product of two primes.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 20382788 + ... + 20382791.

It is an arithmetic number, because the mean of its divisors is an integer number (30574185).

Almost surely, 2^81531158 is an apocalyptic number.

81531158 is a deficient number, since it is larger than the sum of its proper divisors (40765582).

81531158 is a wasteful number, since it uses less digits than its factorization.

81531158 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 40765581.

The product of its digits is 4800, while the sum is 32.

The square root of 81531158 is about 9029.4605597455. The cubic root of 81531158 is about 433.6185673696.

The spelling of 81531158 in words is "eighty-one million, five hundred thirty-one thousand, one hundred fifty-eight".