81721110 has 32 divisors (see below), whose sum is σ = 196368480. Its totient is φ = 21765888.

The previous prime is 81721103. The next prime is 81721121. The reversal of 81721110 is 1112718.

It is a Curzon number.

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 15 ways as a sum of consecutive naturals, for example, 47424 + ... + 49116.

It is an arithmetic number, because the mean of its divisors is an integer number (6136515).

Almost surely, 2^81721110 is an apocalyptic number.

81721110 is an abundant number, since it is smaller than the sum of its proper divisors (114647370).

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

81721110 is a wasteful number, since it uses less digits than its factorization.

81721110 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3312.

The product of its (nonzero) digits is 112, while the sum is 21.

The square root of 81721110 is about 9039.9728981895. The cubic root of 81721110 is about 433.9550556217.

Adding to 81721110 its reverse (1112718), we get a palindrome (82833828).

The spelling of 81721110 in words is "eighty-one million, seven hundred twenty-one thousand, one hundred ten".