81431040 has 160 divisors (see below), whose sum is σ = 272232576. Its totient is φ = 20725760.

The previous prime is 81431039. The next prime is 81431047. The reversal of 81431040 is 4013418.

It is a tau number, because it is divible by the number of its divisors (160).

It is a junction number, because it is equal to n+sod(n) for n = 81430998 and 81431016.

It is not an unprimeable number, because it can be changed into a prime (81431047) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 176410 + ... + 176870.

Almost surely, 2^81431040 is an apocalyptic number.

81431040 is a gapful number since it is divisible by the number (80) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 81431040, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (136116288).

81431040 is an abundant number, since it is smaller than the sum of its proper divisors (190801536).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

81431040 is a wasteful number, since it uses less digits than its factorization.

81431040 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 510 (or 494 counting only the distinct ones).

The product of its (nonzero) digits is 384, while the sum is 21.

The square root of 81431040 is about 9023.9148932157. The cubic root of 81431040 is about 433.4410041454.

Adding to 81431040 its reverse (4013418), we get a palindrome (85444458).

The spelling of 81431040 in words is "eighty-one million, four hundred thirty-one thousand, forty".