81578440 has 16 divisors (see below), whose sum is σ = 183551580. Its totient is φ = 32631360.

The previous prime is 81578423. The next prime is 81578467. The reversal of 81578440 is 4487518.

It can be written as a sum of positive squares in 2 ways, for example, as 76352644 + 5225796 = 8738^2 + 2286^2 .

It is a self number, because there is not a number n which added to its sum of digits gives 81578440.

It is an unprimeable number.

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, 1019691 + ... + 1019770.

Almost surely, 2^81578440 is an apocalyptic number.

It is an amenable number.

81578440 is an abundant number, since it is smaller than the sum of its proper divisors (101973140).

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

81578440 is a wasteful number, since it uses less digits than its factorization.

81578440 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2039472 (or 2039468 counting only the distinct ones).

The product of its (nonzero) digits is 35840, while the sum is 37.

The square root of 81578440 is about 9032.0783876138. The cubic root of 81578440 is about 433.7023733304.

The spelling of 81578440 in words is "eighty-one million, five hundred seventy-eight thousand, four hundred forty".