81691912406 has 8 divisors (see below), whose sum is σ = 131963858544. Its totient is φ = 37703959560.

The previous prime is 81691912391. The next prime is 81691912409. The reversal of 81691912406 is 60421919618.

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

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81691912409) 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, 1570998290 + ... + 1570998341.

It is an arithmetic number, because the mean of its divisors is an integer number (16495482318).

Almost surely, 2^81691912406 is an apocalyptic number.

81691912406 is a deficient number, since it is larger than the sum of its proper divisors (50271946138).

81691912406 is a wasteful number, since it uses less digits than its factorization.

81691912406 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3141996646.

The product of its (nonzero) digits is 186624, while the sum is 47.

The spelling of 81691912406 in words is "eighty-one billion, six hundred ninety-one million, nine hundred twelve thousand, four hundred six".