81937840 has 40 divisors (see below), whose sum is σ = 192487680. Its totient is φ = 32434176.

The previous prime is 81937837. The next prime is 81937879. The reversal of 81937840 is 4873918.

It is a tau number, because it is divible by the number of its divisors (40).

It is a Harshad number since it is a multiple of its sum of digits (40).

It is a junction number, because it is equal to n+sod(n) for n = 81937793 and 81937802.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 2481 + ... + 13039.

It is an arithmetic number, because the mean of its divisors is an integer number (4812192).

Almost surely, 2^81937840 is an apocalyptic number.

81937840 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 81937840, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (96243840).

81937840 is an abundant number, since it is smaller than the sum of its proper divisors (110549840).

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

81937840 is a wasteful number, since it uses less digits than its factorization.

81937840 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 10669 (or 10663 counting only the distinct ones).

The product of its (nonzero) digits is 48384, while the sum is 40.

The square root of 81937840 is about 9051.9522756144. The cubic root of 81937840 is about 434.3383431965.

The spelling of 81937840 in words is "eighty-one million, nine hundred thirty-seven thousand, eight hundred forty".