81353450581 has 24 divisors (see below), whose sum is σ = 97114719744. Its totient is φ = 67605077760.

The previous prime is 81353450561. The next prime is 81353450587. The reversal of 81353450581 is 18505435318.

It is a happy number.

It is not a de Polignac number, because 81353450581 - 2¹⁹ = 81352926293 is a prime.

It is a super-2 number, since 2×81353450581² (a number of 23 digits) contains 22 as substring.

It is a hoax number, since the sum of its digits (43) coincides with the sum of the digits of its distinct prime factors.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81353450587) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 384325 + ... + 557146.

It is an arithmetic number, because the mean of its divisors is an integer number (4046446656).

Almost surely, 2^81353450581 is an apocalyptic number.

It is an amenable number.

81353450581 is a deficient number, since it is larger than the sum of its proper divisors (15761269163).

81353450581 is a wasteful number, since it uses less digits than its factorization.

81353450581 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 941541 (or 941524 counting only the distinct ones).

The product of its (nonzero) digits is 288000, while the sum is 43.

Adding to 81353450581 its reverse (18505435318), we get a palindrome (99858885899).

The spelling of 81353450581 in words is "eighty-one billion, three hundred fifty-three million, four hundred fifty thousand, five hundred eighty-one".