81291405191 has 4 divisors (see below), whose sum is σ = 82320410400. Its totient is φ = 80262399984.

The previous prime is 81291405157. The next prime is 81291405197. The reversal of 81291405191 is 19150419218.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 81291405191 - 2²² = 81287210887 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81291405197) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 514502486 + ... + 514502643.

It is an arithmetic number, because the mean of its divisors is an integer number (20580102600).

Almost surely, 2^81291405191 is an apocalyptic number.

81291405191 is a deficient number, since it is larger than the sum of its proper divisors (1029005209).

81291405191 is a wasteful number, since it uses less digits than its factorization.

81291405191 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1029005208.

The product of its (nonzero) digits is 25920, while the sum is 41.

The spelling of 81291405191 in words is "eighty-one billion, two hundred ninety-one million, four hundred five thousand, one hundred ninety-one".