81986580 has 240 divisors, whose sum is σ = 294552720. Its totient is φ = 18911232.

The previous prime is 81986579. The next prime is 81986591. The reversal of 81986580 is 8568918.

It can be written as a sum of positive squares in 8 ways, for example, as 1633284 + 80353296 = 1278^2 + 8964^2 .

It is a Harshad number since it is a multiple of its sum of digits (45).

It is a Saint-Exupery number, since it is equal to the product of the sides of a Pythagorean triangle: 687 × 663 × 180.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 79 ways as a sum of consecutive naturals, for example, 357906 + ... + 358134.

It is an arithmetic number, because the mean of its divisors is an integer number (1227303).

Almost surely, 2^81986580 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 81986580, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (147276360).

81986580 is an abundant number, since it is smaller than the sum of its proper divisors (212566140).

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

81986580 is a wasteful number, since it uses less digits than its factorization.

81986580 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 280 (or 269 counting only the distinct ones).

The product of its (nonzero) digits is 138240, while the sum is 45.

The square root of 81986580 is about 9054.6441122774. The cubic root of 81986580 is about 434.4244469011.

The spelling of 81986580 in words is "eighty-one million, nine hundred eighty-six thousand, five hundred eighty".