81691750 has 32 divisors (see below), whose sum is σ = 174777408. Its totient is φ = 28008000.

The previous prime is 81691747. The next prime is 81691769. The reversal of 81691750 is 5719618.

It is a congruent number.

It is an unprimeable number.

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 15 ways as a sum of consecutive naturals, for example, 21591 + ... + 25090.

It is an arithmetic number, because the mean of its divisors is an integer number (5461794).

Almost surely, 2^81691750 is an apocalyptic number.

81691750 is an abundant number, since it is smaller than the sum of its proper divisors (93085658).

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

81691750 is a wasteful number, since it uses less digits than its factorization.

81691750 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 46705 (or 46695 counting only the distinct ones).

The product of its (nonzero) digits is 15120, while the sum is 37.

The square root of 81691750 is about 9038.3488536347. The cubic root of 81691750 is about 433.9030802853.

The spelling of 81691750 in words is "eighty-one million, six hundred ninety-one thousand, seven hundred fifty".