81205631 has 8 divisors (see below), whose sum is σ = 87576720. Its totient is φ = 74852352.

The previous prime is 81205627. The next prime is 81205633. The reversal of 81205631 is 13650218.

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

It is a cyclic number.

It is not a de Polignac number, because 81205631 - 2² = 81205627 is a prime.

It is a super-2 number, since 2×81205631² = 13188709012216322, which contains 22 as substring.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 81205631.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81205633) 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, 5936 + ... + 14058.

It is an arithmetic number, because the mean of its divisors is an integer number (10947090).

Almost surely, 2^81205631 is an apocalyptic number.

81205631 is a deficient number, since it is larger than the sum of its proper divisors (6371089).

81205631 is a wasteful number, since it uses less digits than its factorization.

81205631 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 8905.

The product of its (nonzero) digits is 1440, while the sum is 26.

The square root of 81205631 is about 9011.4167032715. The cubic root of 81205631 is about 433.0406990068.

Adding to 81205631 its reverse (13650218), we get a palindrome (94855849).

The spelling of 81205631 in words is "eighty-one million, two hundred five thousand, six hundred thirty-one".