81691049208 has 64 divisors (see below), whose sum is σ = 207814511520. Its totient is φ = 26753126400.

The previous prime is 81691049201. The next prime is 81691049267. The reversal of 81691049208 is 80294019618.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81691049201) 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, 1258116 + ... + 1321452.

Almost surely, 2^81691049208 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 81691049208, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (103907255760).

81691049208 is an abundant number, since it is smaller than the sum of its proper divisors (126123462312).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

81691049208 is a wasteful number, since it uses less digits than its factorization.

81691049208 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 64288 (or 64284 counting only the distinct ones).

The product of its (nonzero) digits is 248832, while the sum is 48.

The spelling of 81691049208 in words is "eighty-one billion, six hundred ninety-one million, forty-nine thousand, two hundred eight".