81380240 has 40 divisors (see below), whose sum is σ = 189865080. Its totient is φ = 32439296.

The previous prime is 81380153. The next prime is 81380251. The reversal of 81380240 is 4208318.

It can be written as a sum of positive squares in 4 ways, for example, as 524176 + 80856064 = 724^2 + 8992^2 .

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

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 23756 + ... + 26964.

It is an arithmetic number, because the mean of its divisors is an integer number (4746627).

Almost surely, 2^81380240 is an apocalyptic number.

81380240 is a gapful number since it is divisible by the number (80) formed by its first and last digit.

It is an amenable number.

81380240 is an abundant number, since it is smaller than the sum of its proper divisors (108484840).

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

81380240 is a wasteful number, since it uses less digits than its factorization.

81380240 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3539 (or 3533 counting only the distinct ones).

The product of its (nonzero) digits is 1536, while the sum is 26.

The square root of 81380240 is about 9021.0997112326. The cubic root of 81380240 is about 433.3508526776.

Adding to 81380240 its reverse (4208318), we get a palindrome (85588558).

The spelling of 81380240 in words is "eighty-one million, three hundred eighty thousand, two hundred forty".