81540431 has 32 divisors (see below), whose sum is σ = 100759680. Its totient is φ = 64512000.

The previous prime is 81540421. The next prime is 81540479. The reversal of 81540431 is 13404518.

It is not a de Polignac number, because 81540431 - 2⁶ = 81540367 is a prime.

It is a super-2 number, since 2×81540431² = 13297683775331522, which contains 22 as substring.

It is a self number, because there is not a number n which added to its sum of digits gives 81540431.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81540401) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 807281 + ... + 807381.

It is an arithmetic number, because the mean of its divisors is an integer number (3148740).

Almost surely, 2^81540431 is an apocalyptic number.

81540431 is a deficient number, since it is larger than the sum of its proper divisors (19219249).

81540431 is a wasteful number, since it uses less digits than its factorization.

81540431 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 275.

The product of its (nonzero) digits is 1920, while the sum is 26.

The square root of 81540431 is about 9029.9740309704. The cubic root of 81540431 is about 433.6350060443.

Adding to 81540431 its reverse (13404518), we get a palindrome (94944949).

The spelling of 81540431 in words is "eighty-one million, five hundred forty thousand, four hundred thirty-one".