81578855 has 4 divisors (see below), whose sum is σ = 97894632. Its totient is φ = 65263080.

The previous prime is 81578839. The next prime is 81578857. The reversal of 81578855 is 55887518.

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

It is not a de Polignac number, because 81578855 - 2⁴ = 81578839 is a prime.

It is a super-2 number, since 2×81578855² = 13310219166222050, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81578857) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 8157881 + ... + 8157890.

It is an arithmetic number, because the mean of its divisors is an integer number (24473658).

Almost surely, 2^81578855 is an apocalyptic number.

81578855 is a deficient number, since it is larger than the sum of its proper divisors (16315777).

81578855 is a wasteful number, since it uses less digits than its factorization.

81578855 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 16315776.

The product of its digits is 448000, while the sum is 47.

The square root of 81578855 is about 9032.1013612559. The cubic root of 81578855 is about 433.7031087624.

The spelling of 81578855 in words is "eighty-one million, five hundred seventy-eight thousand, eight hundred fifty-five".