81691910090 has 32 divisors (see below), whose sum is σ = 168063068160. Its totient is φ = 28006798464.

The previous prime is 81691910063. The next prime is 81691910119. The reversal of 81691910090 is 9001919618.

It is a Curzon number.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 1409606 + ... + 1466414.

It is an arithmetic number, because the mean of its divisors is an integer number (5251970880).

Almost surely, 2^81691910090 is an apocalyptic number.

81691910090 is an abundant number, since it is smaller than the sum of its proper divisors (86371158070).

81691910090 is a wasteful number, since it uses less digits than its factorization.

81691910090 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 77366.

The product of its (nonzero) digits is 34992, while the sum is 44.

The spelling of 81691910090 in words is "eighty-one billion, six hundred ninety-one million, nine hundred ten thousand, ninety".