81987578478 has 48 divisors (see below), whose sum is σ = 202557556656. Its totient is φ = 23743008000.

The previous prime is 81987578447. The next prime is 81987578527. The reversal of 81987578478 is 87487578918.

81987578478 is a `hidden beast` number, since 8 + 1 + 9 + 8 + 7 + 578 + 47 + 8 = 666.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 10301148 + ... + 10309103.

It is an arithmetic number, because the mean of its divisors is an integer number (4219949097).

Almost surely, 2^81987578478 is an apocalyptic number.

81987578478 is an abundant number, since it is smaller than the sum of its proper divisors (120569978178).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

81987578478 is a wasteful number, since it uses less digits than its factorization.

81987578478 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 20610289 (or 20610286 counting only the distinct ones).

The product of its digits is 252887040, while the sum is 72.

The spelling of 81987578478 in words is "eighty-one billion, nine hundred eighty-seven million, five hundred seventy-eight thousand, four hundred seventy-eight".