81404593 has 2 divisors, whose sum is σ = 81404594. Its totient is φ = 81404592.

The previous prime is 81404591. The next prime is 81404621. The reversal of 81404593 is 39540418.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 51022449 + 30382144 = 7143^2 + 5512^2 .

It is a cyclic number.

It is not a de Polignac number, because 81404593 - 2¹ = 81404591 is a prime.

It is a super-3 number, since 3×81404593³ (a number of 25 digits) contains 333 as substring. Note that it is a super-d number also for d = 2.

Together with 81404591, it forms a pair of twin primes.

It is not a weakly prime, because it can be changed into another prime (81404591) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40702296 + 40702297.

It is an arithmetic number, because the mean of its divisors is an integer number (40702297).

Almost surely, 2^81404593 is an apocalyptic number.

It is an amenable number.

81404593 is a deficient number, since it is larger than the sum of its proper divisors (1).

81404593 is an equidigital number, since it uses as much as digits as its factorization.

81404593 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 17280, while the sum is 34.

The square root of 81404593 is about 9022.4493902709. The cubic root of 81404593 is about 433.3940750487.

The spelling of 81404593 in words is "eighty-one million, four hundred four thousand, five hundred ninety-three".