81800555 has 4 divisors (see below), whose sum is σ = 98160672. Its totient is φ = 65440440.

The previous prime is 81800533. The next prime is 81800557. The reversal of 81800555 is 55500818.

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

It is not a de Polignac number, because 81800555 - 2¹² = 81796459 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (81800557) 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, 8180051 + ... + 8180060.

It is an arithmetic number, because the mean of its divisors is an integer number (24540168).

Almost surely, 2^81800555 is an apocalyptic number.

81800555 is a deficient number, since it is larger than the sum of its proper divisors (16360117).

81800555 is a wasteful number, since it uses less digits than its factorization.

81800555 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 16360116.

The product of its (nonzero) digits is 8000, while the sum is 32.

The square root of 81800555 is about 9044.3659258126. The cubic root of 81800555 is about 434.0956328999.

The spelling of 81800555 in words is "eighty-one million, eight hundred thousand, five hundred fifty-five".