81171767391 has 16 divisors (see below), whose sum is σ = 127150181760. Its totient is φ = 45410778720.

The previous prime is 81171767381. The next prime is 81171767401. The reversal of 81171767391 is 19376717118.

It is an interprime number because it is at equal distance from previous prime (81171767381) and next prime (81171767401).

It is not a de Polignac number, because 81171767391 - 2¹³ = 81171759199 is a prime.

It is a super-2 number, since 2×81171767391² (a number of 23 digits) contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81171767381) 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, 94605361 + ... + 94606218.

It is an arithmetic number, because the mean of its divisors is an integer number (7946886360).

Almost surely, 2^81171767391 is an apocalyptic number.

81171767391 is a deficient number, since it is larger than the sum of its proper divisors (45978414369).

81171767391 is a wasteful number, since it uses less digits than its factorization.

81171767391 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 189211606.

The product of its digits is 444528, while the sum is 51.

The spelling of 81171767391 in words is "eighty-one billion, one hundred seventy-one million, seven hundred sixty-seven thousand, three hundred ninety-one".