81291406685 has 8 divisors (see below), whose sum is σ = 97576634880. Its totient is φ = 65015160784.

The previous prime is 81291406681. The next prime is 81291406687. The reversal of 81291406685 is 58660419218.

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

It is a cyclic number.

It is not a de Polignac number, because 81291406685 - 2² = 81291406681 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81291406681) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 2225645 + ... + 2261874.

It is an arithmetic number, because the mean of its divisors is an integer number (12197079360).

Almost surely, 2^81291406685 is an apocalyptic number.

It is an amenable number.

81291406685 is a deficient number, since it is larger than the sum of its proper divisors (16285228195).

81291406685 is a wasteful number, since it uses less digits than its factorization.

81291406685 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4491147.

The product of its (nonzero) digits is 829440, while the sum is 50.

The spelling of 81291406685 in words is "eighty-one billion, two hundred ninety-one million, four hundred six thousand, six hundred eighty-five".