81491136005 has 16 divisors (see below), whose sum is σ = 99501782400. Its totient is φ = 64052518080.

The previous prime is 81491135989. The next prime is 81491136007. The reversal of 81491136005 is 50063119418.

It is not a de Polignac number, because 81491136005 - 2⁴ = 81491135989 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 81491136005.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81491136007) 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, 464711 + ... + 615579.

It is an arithmetic number, because the mean of its divisors is an integer number (6218861400).

Almost surely, 2^81491136005 is an apocalyptic number.

It is an amenable number.

81491136005 is a deficient number, since it is larger than the sum of its proper divisors (18010646395).

81491136005 is a wasteful number, since it uses less digits than its factorization.

81491136005 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 152764.

The product of its (nonzero) digits is 25920, while the sum is 38.

The spelling of 81491136005 in words is "eighty-one billion, four hundred ninety-one million, one hundred thirty-six thousand, five".