81558440 has 32 divisors (see below), whose sum is σ = 189837000. Its totient is φ = 31497984.

The previous prime is 81558439. The next prime is 81558461. The reversal of 81558440 is 4485518.

It can be written as a sum of positive squares in 4 ways, for example, as 52678564 + 28879876 = 7258^2 + 5374^2 .

It is a self number, because there is not a number n which added to its sum of digits gives 81558440.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 33995 + ... + 36314.

Almost surely, 2^81558440 is an apocalyptic number.

It is an amenable number.

81558440 is an abundant number, since it is smaller than the sum of its proper divisors (108278560).

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

81558440 is a wasteful number, since it uses less digits than its factorization.

81558440 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 70349 (or 70345 counting only the distinct ones).

The product of its (nonzero) digits is 25600, while the sum is 35.

The square root of 81558440 is about 9030.9711548648. The cubic root of 81558440 is about 433.6669278687. Note that the first 3 decimals are identical.

The spelling of 81558440 in words is "eighty-one million, five hundred fifty-eight thousand, four hundred forty".