81390405 has 16 divisors (see below), whose sum is σ = 130956480. Its totient is φ = 43164288.

The previous prime is 81390383. The next prime is 81390473. The reversal of 81390405 is 50409318.

It is not a de Polignac number, because 81390405 - 2⁷ = 81390277 is a prime.

It is a Curzon number.

It is a congruent 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, 12472 + ... + 17841.

It is an arithmetic number, because the mean of its divisors is an integer number (8184780).

Almost surely, 2^81390405 is an apocalyptic number.

It is an amenable number.

81390405 is a deficient number, since it is larger than the sum of its proper divisors (49566075).

81390405 is a wasteful number, since it uses less digits than its factorization.

81390405 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 30500.

The product of its (nonzero) digits is 4320, while the sum is 30.

The square root of 81390405 is about 9021.6630950175. The cubic root of 81390405 is about 433.3688948462.

The spelling of 81390405 in words is "eighty-one million, three hundred ninety thousand, four hundred five".