81448640 has 112 divisors (see below), whose sum is σ = 238792512. Its totient is φ = 25767936.

The previous prime is 81448637. The next prime is 81448643. The reversal of 81448640 is 4684418.

It is an interprime number because it is at equal distance from previous prime (81448637) and next prime (81448643).

It is a tau number, because it is divible by the number of its divisors (112).

It is a Harshad number since it is a multiple of its sum of digits (35).

It is a self number, because there is not a number n which added to its sum of digits gives 81448640.

It is not an unprimeable number, because it can be changed into a prime (81448643) 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 15 ways as a sum of consecutive naturals, for example, 27722 + ... + 30518.

It is an arithmetic number, because the mean of its divisors is an integer number (2132076).

Almost surely, 2^81448640 is an apocalyptic number.

81448640 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 81448640, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (119396256).

81448640 is an abundant number, since it is smaller than the sum of its proper divisors (157343872).

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

81448640 is a wasteful number, since it uses less digits than its factorization.

81448640 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2834 (or 2824 counting only the distinct ones).

The product of its (nonzero) digits is 24576, while the sum is 35.

The square root of 81448640 is about 9024.8900270308. The cubic root of 81448640 is about 433.4722289795.

The spelling of 81448640 in words is "eighty-one million, four hundred forty-eight thousand, six hundred forty".