81909756 has 18 divisors (see below), whose sum is σ = 207049752. Its totient is φ = 27303240.

The previous prime is 81909733. The next prime is 81909761. The reversal of 81909756 is 65790918.

It is a tau number, because it is divible by the number of its divisors (18).

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 5 ways as a sum of consecutive naturals, for example, 1137600 + ... + 1137671.

It is an arithmetic number, because the mean of its divisors is an integer number (11502764).

Almost surely, 2^81909756 is an apocalyptic number.

It is an amenable number.

81909756 is an abundant number, since it is smaller than the sum of its proper divisors (125139996).

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

81909756 is a wasteful number, since it uses less digits than its factorization.

81909756 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2275281 (or 2275276 counting only the distinct ones).

The product of its (nonzero) digits is 136080, while the sum is 45.

The square root of 81909756 is about 9050.4008750994. The cubic root of 81909756 is about 434.2887147143.

The spelling of 81909756 in words is "eighty-one million, nine hundred nine thousand, seven hundred fifty-six".