81693931840 has 224 divisors, whose sum is σ = 208657886976. Its totient is φ = 30391173120.

The previous prime is 81693931829. The next prime is 81693931841. The reversal of 81693931840 is 4813939618.

It is a happy number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81693931841) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 92728200 + ... + 92729080.

It is an arithmetic number, because the mean of its divisors is an integer number (931508424).

Almost surely, 2^81693931840 is an apocalyptic number.

81693931840 is a gapful number since it is divisible by the number (80) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 81693931840, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (104328943488).

81693931840 is an abundant number, since it is smaller than the sum of its proper divisors (126963955136).

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

81693931840 is a wasteful number, since it uses less digits than its factorization.

81693931840 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1257 (or 1247 counting only the distinct ones).

The product of its (nonzero) digits is 1119744, while the sum is 52.

The spelling of 81693931840 in words is "eighty-one billion, six hundred ninety-three million, nine hundred thirty-one thousand, eight hundred forty".