81420042240 has 480 divisors, whose sum is σ = 292732513920. Its totient is φ = 21469593600.

The previous prime is 81420042229. The next prime is 81420042247. The reversal of 81420042240 is 4224002418.

It is a tau number, because it is divible by the number of its divisors (480).

It is a Harshad number since it is a multiple of its sum of digits (27).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81420042247) by changing a digit.

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 31 ways as a sum of consecutive naturals, for example, 289750900 + ... + 289751180.

It is an arithmetic number, because the mean of its divisors is an integer number (609859404).

Almost surely, 2^81420042240 is an apocalyptic number.

81420042240 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 81420042240, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (146366256960).

81420042240 is an abundant number, since it is smaller than the sum of its proper divisors (211312471680).

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

81420042240 is a wasteful number, since it uses less digits than its factorization.

81420042240 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 454 (or 422 counting only the distinct ones).

The product of its (nonzero) digits is 4096, while the sum is 27.

Adding to 81420042240 its reverse (4224002418), we get a palindrome (85644044658).

The spelling of 81420042240 in words is "eighty-one billion, four hundred twenty million, forty-two thousand, two hundred forty".