81375840 has 576 divisors, whose sum is σ = 369847296. Its totient is φ = 16422912.

The previous prime is 81375793. The next prime is 81375851. The reversal of 81375840 is 4857318.

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 = 81375795 and 81375804.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 95 ways as a sum of consecutive naturals, for example, 3538069 + ... + 3538091.

It is an arithmetic number, because the mean of its divisors is an integer number (642096).

Almost surely, 2^81375840 is an apocalyptic number.

81375840 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 81375840, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (184923648).

81375840 is an abundant number, since it is smaller than the sum of its proper divisors (288471456).

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

81375840 is a wasteful number, since it uses less digits than its factorization.

81375840 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 73 (or 53 counting only the distinct ones).

The product of its (nonzero) digits is 26880, while the sum is 36.

The square root of 81375840 is about 9020.8558352298. The cubic root of 81375840 is about 433.3430425175.

It can be divided in two parts, 81375 and 840, that added together give a triangular number (82215 = T₄₀₅).

The spelling of 81375840 in words is "eighty-one million, three hundred seventy-five thousand, eight hundred forty".