81129405 has 16 divisors (see below), whose sum is σ = 148351104. Its totient is φ = 37087680.

The previous prime is 81129401. The next prime is 81129413. The reversal of 81129405 is 50492118.

It is a happy number.

It is not a de Polignac number, because 81129405 - 2² = 81129401 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81129401) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 386226 + ... + 386435.

It is an arithmetic number, because the mean of its divisors is an integer number (9271944).

Almost surely, 2^81129405 is an apocalyptic number.

It is an amenable number.

81129405 is a deficient number, since it is larger than the sum of its proper divisors (67221699).

81129405 is a wasteful number, since it uses less digits than its factorization.

81129405 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 772676.

The product of its (nonzero) digits is 2880, while the sum is 30.

The square root of 81129405 is about 9007.1862976181. The cubic root of 81129405 is about 432.9051612221.

The spelling of 81129405 in words is "eighty-one million, one hundred twenty-nine thousand, four hundred five".