81891219 has 16 divisors (see below), whose sum is σ = 112651520. Its totient is φ = 52889760.

The previous prime is 81891211. The next prime is 81891223. The reversal of 81891219 is 91219818.

It is not a de Polignac number, because 81891219 - 2³ = 81891211 is a prime.

It is a super-2 number, since 2×81891219² = 13412343498611922, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (81891211) 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, 8922 + ... + 15600.

It is an arithmetic number, because the mean of its divisors is an integer number (7040720).

Almost surely, 2^81891219 is an apocalyptic number.

81891219 is a deficient number, since it is larger than the sum of its proper divisors (30760301).

81891219 is a wasteful number, since it uses less digits than its factorization.

81891219 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 6810.

The product of its digits is 10368, while the sum is 39.

The square root of 81891219 is about 9049.3767188685. The cubic root of 81891219 is about 434.2559509441.

The spelling of 81891219 in words is "eighty-one million, eight hundred ninety-one thousand, two hundred nineteen".