81408518 has 4 divisors (see below), whose sum is σ = 122112780. Its totient is φ = 40704258.

The previous prime is 81408517. The next prime is 81408527. The reversal of 81408518 is 81580418.

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

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81408517) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 20352128 + ... + 20352131.

It is an arithmetic number, because the mean of its divisors is an integer number (30528195).

Almost surely, 2^81408518 is an apocalyptic number.

81408518 is a deficient number, since it is larger than the sum of its proper divisors (40704262).

81408518 is a wasteful number, since it uses less digits than its factorization.

81408518 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 40704261.

The product of its (nonzero) digits is 10240, while the sum is 35.

The square root of 81408518 is about 9022.6669006453. Note that the first 3 decimals coincide. The cubic root of 81408518 is about 433.4010404395.

The spelling of 81408518 in words is "eighty-one million, four hundred eight thousand, five hundred eighteen".