81631281 has 8 divisors (see below), whose sum is σ = 108957024. Its totient is φ = 54363200.

The previous prime is 81631273. The next prime is 81631309. The reversal of 81631281 is 18213618.

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 81631281 - 2³ = 81631273 is a prime.

It is a super-2 number, since 2×81631281² = 13327332075401922, which contains 22 as substring.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (81631211) 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 7 ways as a sum of consecutive naturals, for example, 10995 + ... + 16856.

It is an arithmetic number, because the mean of its divisors is an integer number (13619628).

Almost surely, 2^81631281 is an apocalyptic number.

It is an amenable number.

81631281 is a deficient number, since it is larger than the sum of its proper divisors (27325743).

81631281 is a wasteful number, since it uses less digits than its factorization.

81631281 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 28831.

The product of its digits is 2304, while the sum is 30.

The square root of 81631281 is about 9035.0030990587. The cubic root of 81631281 is about 433.7959941482.

Adding to 81631281 its reverse (18213618), we get a palindrome (99844899).

The spelling of 81631281 in words is "eighty-one million, six hundred thirty-one thousand, two hundred eighty-one".