81553603 has 4 divisors (see below), whose sum is σ = 81636400. Its totient is φ = 81470808.

The previous prime is 81553579. The next prime is 81553613. The reversal of 81553603 is 30635518.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 30635518 = 2 ⋅15317759.

It is a cyclic number.

It is not a de Polignac number, because 81553603 - 2⁹ = 81553091 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (81553613) 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 3 ways as a sum of consecutive naturals, for example, 39903 + ... + 41896.

It is an arithmetic number, because the mean of its divisors is an integer number (20409100).

Almost surely, 2^81553603 is an apocalyptic number.

81553603 is a deficient number, since it is larger than the sum of its proper divisors (82797).

81553603 is an equidigital number, since it uses as much as digits as its factorization.

81553603 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 82796.

The product of its (nonzero) digits is 10800, while the sum is 31.

The square root of 81553603 is about 9030.7033502380. The cubic root of 81553603 is about 433.6583545136.

The spelling of 81553603 in words is "eighty-one million, five hundred fifty-three thousand, six hundred three".