81405560 has 32 divisors (see below), whose sum is σ = 184852800. Its totient is φ = 32261760.

The previous prime is 81405529. The next prime is 81405563. The reversal of 81405560 is 6550418.

It is a happy number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81405563) 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, 4976 + ... + 13695.

It is an arithmetic number, because the mean of its divisors is an integer number (5776650).

Almost surely, 2^81405560 is an apocalyptic number.

It is an amenable number.

81405560 is an abundant number, since it is smaller than the sum of its proper divisors (103447240).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

81405560 is a wasteful number, since it uses less digits than its factorization.

81405560 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 18791 (or 18787 counting only the distinct ones).

The product of its (nonzero) digits is 4800, while the sum is 29.

The square root of 81405560 is about 9022.5029786640. The cubic root of 81405560 is about 433.3957911288.

Adding to 81405560 its reverse (6550418), we get a palindrome (87955978).

The spelling of 81405560 in words is "eighty-one million, four hundred five thousand, five hundred sixty".