81891403 has 4 divisors (see below), whose sum is σ = 89336088. Its totient is φ = 74446720.

The previous prime is 81891379. The next prime is 81891419. The reversal of 81891403 is 30419818.

It is a happy number.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 81891403 - 2⁵ = 81891371 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (81892403) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 3722326 + ... + 3722347.

It is an arithmetic number, because the mean of its divisors is an integer number (22334022).

Almost surely, 2^81891403 is an apocalyptic number.

81891403 is a deficient number, since it is larger than the sum of its proper divisors (7444685).

81891403 is a wasteful number, since it uses less digits than its factorization.

81891403 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7444684.

The product of its (nonzero) digits is 6912, while the sum is 34.

The square root of 81891403 is about 9049.3868853089. The cubic root of 81891403 is about 434.2562761846.

The spelling of 81891403 in words is "eighty-one million, eight hundred ninety-one thousand, four hundred three".