81553903 has 4 divisors (see below), whose sum is σ = 81575208. Its totient is φ = 81532600.

The previous prime is 81553877. The next prime is 81553907. The reversal of 81553903 is 30935518.

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

It is a cyclic number.

It is not a de Polignac number, because 81553903 - 2⁹ = 81553391 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81553907) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 3148 + ... + 13153.

It is an arithmetic number, because the mean of its divisors is an integer number (20393802).

Almost surely, 2^81553903 is an apocalyptic number.

81553903 is a deficient number, since it is larger than the sum of its proper divisors (21305).

81553903 is a wasteful number, since it uses less digits than its factorization.

81553903 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 21304.

The product of its (nonzero) digits is 16200, while the sum is 34.

The square root of 81553903 is about 9030.7199602247. The cubic root of 81553903 is about 433.6588862594.

The spelling of 81553903 in words is "eighty-one million, five hundred fifty-three thousand, nine hundred three".