81541778457 has 4 divisors (see below), whose sum is σ = 108722371280. Its totient is φ = 54361185636.

The previous prime is 81541778449. The next prime is 81541778473. The reversal of 81541778457 is 75487714518.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is not a de Polignac number, because 81541778457 - 2³ = 81541778449 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 81541778397 and 81541778406.

It is not an unprimeable number, because it can be changed into a prime (81541778497) 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 3 ways as a sum of consecutive naturals, for example, 13590296407 + ... + 13590296412.

It is an arithmetic number, because the mean of its divisors is an integer number (27180592820).

Almost surely, 2^81541778457 is an apocalyptic number.

It is an amenable number.

81541778457 is a deficient number, since it is larger than the sum of its proper divisors (27180592823).

81541778457 is a wasteful number, since it uses less digits than its factorization.

81541778457 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 27180592822.

The product of its digits is 8780800, while the sum is 57.

The spelling of 81541778457 in words is "eighty-one billion, five hundred forty-one million, seven hundred seventy-eight thousand, four hundred fifty-seven".