81293940 has 216 divisors, whose sum is σ = 309352680. Its totient is φ = 17127936.

The previous prime is 81293909. The next prime is 81293941. The reversal of 81293940 is 4939218.

It can be written as a sum of positive squares in 4 ways, for example, as 509796 + 80784144 = 714^2 + 8988^2 .

It is a Harshad number since it is a multiple of its sum of digits (36).

It is a junction number, because it is equal to n+sod(n) for n = 81293895 and 81293904.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81293941) 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 71 ways as a sum of consecutive naturals, for example, 114306 + ... + 115014.

Almost surely, 2^81293940 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 81293940, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (154676340).

81293940 is an abundant number, since it is smaller than the sum of its proper divisors (228058740).

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

81293940 is a wasteful number, since it uses less digits than its factorization.

81293940 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 751 (or 739 counting only the distinct ones).

The product of its (nonzero) digits is 15552, while the sum is 36.

The square root of 81293940 is about 9016.3152118812. The cubic root of 81293940 is about 433.1976156180.

The spelling of 81293940 in words is "eighty-one million, two hundred ninety-three thousand, nine hundred forty".