81931500 has 360 divisors, whose sum is σ = 324516192. Its totient is φ = 17625600.

The previous prime is 81931463. The next prime is 81931501. The reversal of 81931500 is 513918.

It is a Harshad number since it is a multiple of its sum of digits (27).

It is not an unprimeable number, because it can be changed into a prime (81931501) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 119 ways as a sum of consecutive naturals, for example, 4819492 + ... + 4819508.

Almost surely, 2^81931500 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 81931500, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (162258096).

81931500 is an abundant number, since it is smaller than the sum of its proper divisors (242584692).

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

81931500 is a wasteful number, since it uses less digits than its factorization.

81931500 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 72 (or 34 counting only the distinct ones).

The product of its (nonzero) digits is 1080, while the sum is 27.

The square root of 81931500 is about 9051.6020681424. The cubic root of 81931500 is about 434.3271404924.

The spelling of 81931500 in words is "eighty-one million, nine hundred thirty-one thousand, five hundred".