81228990005 has 4 divisors (see below), whose sum is σ = 97474788012. Its totient is φ = 64983192000.

The previous prime is 81228989987. The next prime is 81228990041. The reversal of 81228990005 is 50009982218.

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

It can be written as a sum of positive squares in 2 ways, for example, as 63846677041 + 17382312964 = 252679^2 + 131842^2 .

It is not a de Polignac number, because 81228990005 - 2⁸ = 81228989749 is a prime.

It is a Duffinian number.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 8122898996 + ... + 8122899005.

It is an arithmetic number, because the mean of its divisors is an integer number (24368697003).

Almost surely, 2^81228990005 is an apocalyptic number.

It is an amenable number.

81228990005 is a deficient number, since it is larger than the sum of its proper divisors (16245798007).

81228990005 is a wasteful number, since it uses less digits than its factorization.

81228990005 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 16245798006.

The product of its (nonzero) digits is 103680, while the sum is 44.

Adding to 81228990005 its sum of digits (44), we get a square (81228990049 = 285007²).

The spelling of 81228990005 in words is "eighty-one billion, two hundred twenty-eight million, nine hundred ninety thousand, five".