81491542557 has 8 divisors (see below), whose sum is σ = 108871406784. Its totient is φ = 54219686688.

The previous prime is 81491542549. The next prime is 81491542571. The reversal of 81491542557 is 75524519418.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 81491542557 - 2³ = 81491542549 is a prime.

It is a super-3 number, since 3×81491542557³ (a number of 34 digits) contains 333 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81491542537) 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 7 ways as a sum of consecutive naturals, for example, 27000328 + ... + 27003345.

It is an arithmetic number, because the mean of its divisors is an integer number (13608925848).

Almost surely, 2^81491542557 is an apocalyptic number.

It is an amenable number.

81491542557 is a deficient number, since it is larger than the sum of its proper divisors (27379864227).

81491542557 is a wasteful number, since it uses less digits than its factorization.

81491542557 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 54004179.

The product of its digits is 2016000, while the sum is 51.

The spelling of 81491542557 in words is "eighty-one billion, four hundred ninety-one million, five hundred forty-two thousand, five hundred fifty-seven".