81553418 has 4 divisors (see below), whose sum is σ = 122330130. Its totient is φ = 40776708.

The previous prime is 81553397. The next prime is 81553457. The reversal of 81553418 is 81435518.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 81435518 = 2 ⋅40717759.

It can be written as a sum of positive squares in only one way, i.e., 46471489 + 35081929 = 6817^2 + 5923^2 .

It is an unprimeable number.

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, 20388353 + ... + 20388356.

Almost surely, 2^81553418 is an apocalyptic number.

81553418 is a deficient number, since it is larger than the sum of its proper divisors (40776712).

81553418 is a wasteful number, since it uses less digits than its factorization.

81553418 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 40776711.

The product of its digits is 19200, while the sum is 35.

The square root of 81553418 is about 9030.6931073977. The cubic root of 81553418 is about 433.6580266031.

The spelling of 81553418 in words is "eighty-one million, five hundred fifty-three thousand, four hundred eighteen".