81909091 has 8 divisors (see below), whose sum is σ = 89751744. Its totient is φ = 74132520.

The previous prime is 81909089. The next prime is 81909127. The reversal of 81909091 is 19090918.

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

It is not a de Polignac number, because 81909091 - 2¹ = 81909089 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 81909091.

It is not an unprimeable number, because it can be changed into a prime (81909011) 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, 13905 + ... + 18898.

It is an arithmetic number, because the mean of its divisors is an integer number (11218968).

Almost surely, 2^81909091 is an apocalyptic number.

81909091 is a deficient number, since it is larger than the sum of its proper divisors (7842653).

81909091 is a wasteful number, since it uses less digits than its factorization.

81909091 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 33041.

The product of its (nonzero) digits is 5832, while the sum is 37.

The square root of 81909091 is about 9050.3641363207. The cubic root of 81909091 is about 434.2875394258.

The spelling of 81909091 in words is "eighty-one million, nine hundred nine thousand, ninety-one".