81665500 has 48 divisors (see below), whose sum is σ = 203845824. Its totient is φ = 27998400.

The previous prime is 81665489. The next prime is 81665509. The reversal of 81665500 is 556618.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81665509) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 8167 + ... + 15166.

It is an arithmetic number, because the mean of its divisors is an integer number (4246788).

Almost surely, 2^81665500 is an apocalyptic number.

It is an amenable number.

81665500 is an abundant number, since it is smaller than the sum of its proper divisors (122180324).

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

81665500 is a wasteful number, since it uses less digits than its factorization.

81665500 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 23359 (or 23347 counting only the distinct ones).

The product of its (nonzero) digits is 7200, while the sum is 31.

The square root of 81665500 is about 9036.8965911977. The cubic root of 81665500 is about 433.8565999653.

The spelling of 81665500 in words is "eighty-one million, six hundred sixty-five thousand, five hundred".