81266580 has 36 divisors (see below), whose sum is σ = 246509172. Its totient is φ = 21671040.

The previous prime is 81266573. The next prime is 81266587. The reversal of 81266580 is 8566218.

It is a happy number.

81266580 is a `hidden beast` number, since 8 + 12 + 66 + 580 = 666.

It is an interprime number because it is at equal distance from previous prime (81266573) and next prime (81266587).

It can be written as a sum of positive squares in 2 ways, for example, as 34644996 + 46621584 = 5886^2 + 6828^2 .

It is a tau number, because it is divible by the number of its divisors (36).

It is a Harshad number since it is a multiple of its sum of digits (36).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81266587) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 225561 + ... + 225920.

It is an arithmetic number, because the mean of its divisors is an integer number (6847477).

Almost surely, 2^81266580 is an apocalyptic number.

It is an amenable number.

81266580 is an abundant number, since it is smaller than the sum of its proper divisors (165242592).

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

81266580 is a wasteful number, since it uses less digits than its factorization.

81266580 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 451496 (or 451491 counting only the distinct ones).

The product of its (nonzero) digits is 23040, while the sum is 36.

The square root of 81266580 is about 9014.7978346716. The cubic root of 81266580 is about 433.1490116808.

It can be divided in two parts, 8126 and 6580, that added together give a triangular number (14706 = T₁₇₁).

The spelling of 81266580 in words is "eighty-one million, two hundred sixty-six thousand, five hundred eighty".