81656280 has 48 divisors (see below), whose sum is σ = 265384080. Its totient is φ = 21774912.

The previous prime is 81656273. The next prime is 81656291. The reversal of 81656280 is 8265618.

It is a happy number.

81656280 is a `hidden beast` number, since 8 + 16 + 562 + 80 = 666.

It is a super-3 number, since 3×81656280³ (a number of 25 digits) contains 333 as substring.

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

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 113052 + ... + 113771.

It is an arithmetic number, because the mean of its divisors is an integer number (5528835).

Almost surely, 2^81656280 is an apocalyptic number.

It is an amenable number.

81656280 is an abundant number, since it is smaller than the sum of its proper divisors (183727800).

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

81656280 is a wasteful number, since it uses less digits than its factorization.

81656280 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 226840 (or 226833 counting only the distinct ones).

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

The square root of 81656280 is about 9036.3864459196. The cubic root of 81656280 is about 433.8402719426.

The spelling of 81656280 in words is "eighty-one million, six hundred fifty-six thousand, two hundred eighty".