81491535291 has 16 divisors (see below), whose sum is σ = 117494682624. Its totient is φ = 50044028544.

The previous prime is 81491535271. The next prime is 81491535311. The reversal of 81491535291 is 19253519418.

It is an interprime number because it is at equal distance from previous prime (81491535271) and next prime (81491535311).

It is not a de Polignac number, because 81491535291 - 2¹⁸ = 81491273147 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 81491535291.

It is not an unprimeable number, because it can be changed into a prime (81491535271) 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, 16996255 + ... + 17001048.

It is an arithmetic number, because the mean of its divisors is an integer number (7343417664).

Almost surely, 2^81491535291 is an apocalyptic number.

81491535291 is a deficient number, since it is larger than the sum of its proper divisors (36003147333).

81491535291 is a wasteful number, since it uses less digits than its factorization.

81491535291 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 33997370.

The product of its digits is 388800, while the sum is 48.

The spelling of 81491535291 in words is "eighty-one billion, four hundred ninety-one million, five hundred thirty-five thousand, two hundred ninety-one".