81491136369 has 8 divisors (see below), whose sum is σ = 115046310240. Its totient is φ = 51131693376.

The previous prime is 81491136367. The next prime is 81491136469. The reversal of 81491136369 is 96363119418.

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

It is not a de Polignac number, because 81491136369 - 2¹ = 81491136367 is a prime.

It is a super-2 number, since 2×81491136369² (a number of 23 digits) contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (51), and also a Moran number because the ratio is a prime number: 1597865419 = 81491136369 / (8 + 1 + 4 + 9 + 1 + 1 + 3 + 6 + 3 + 6 + 9).

It is not an unprimeable number, because it can be changed into a prime (81491136361) 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, 798932659 + ... + 798932760.

It is an arithmetic number, because the mean of its divisors is an integer number (14380788780).

Almost surely, 2^81491136369 is an apocalyptic number.

It is an amenable number.

81491136369 is a deficient number, since it is larger than the sum of its proper divisors (33555173871).

81491136369 is a wasteful number, since it uses less digits than its factorization.

81491136369 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1597865439.

The product of its digits is 839808, while the sum is 51.

The spelling of 81491136369 in words is "eighty-one billion, four hundred ninety-one million, one hundred thirty-six thousand, three hundred sixty-nine".