81581631 has 8 divisors (see below), whose sum is σ = 109010304. Its totient is φ = 54270360.

The previous prime is 81581629. The next prime is 81581659. The reversal of 81581631 is 13618518.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 81581631 - 2¹ = 81581629 is a prime.

It is a super-2 number, since 2×81581631² = 13311125033240322, which contains 22 as substring.

It is a junction number, because it is equal to n+sod(n) for n = 81581592 and 81581601.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81581131) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 27715 + ... + 30516.

It is an arithmetic number, because the mean of its divisors is an integer number (13626288).

Almost surely, 2^81581631 is an apocalyptic number.

81581631 is a deficient number, since it is larger than the sum of its proper divisors (27428673).

81581631 is a wasteful number, since it uses less digits than its factorization.

81581631 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 58701.

The product of its digits is 5760, while the sum is 33.

The square root of 81581631 is about 9032.2550340433. The cubic root of 81581631 is about 433.7080281179.

The spelling of 81581631 in words is "eighty-one million, five hundred eighty-one thousand, six hundred thirty-one".