81990784261 has 8 divisors (see below), whose sum is σ = 85896465984. Its totient is φ = 78113508000.

The previous prime is 81990784259. The next prime is 81990784313. The reversal of 81990784261 is 16248709918.

It is a happy number.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 81990784261 - 2¹ = 81990784259 is a prime.

It is a super-2 number, since 2×81990784261² (a number of 23 digits) contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81990784241) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 7095456 + ... + 7107001.

It is an arithmetic number, because the mean of its divisors is an integer number (10737058248).

Almost surely, 2^81990784261 is an apocalyptic number.

It is an amenable number.

81990784261 is a deficient number, since it is larger than the sum of its proper divisors (3905681723).

81990784261 is a wasteful number, since it uses less digits than its factorization.

81990784261 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 14202731.

The product of its (nonzero) digits is 1741824, while the sum is 55.

The spelling of 81990784261 in words is "eighty-one billion, nine hundred ninety million, seven hundred eighty-four thousand, two hundred sixty-one".