81551040 has 224 divisors, whose sum is σ = 289681920. Its totient is φ = 19316736.

The previous prime is 81551033. The next prime is 81551051. The reversal of 81551040 is 4015518.

It is a Harshad number since it is a multiple of its sum of digits (24).

It is a self number, because there is not a number n which added to its sum of digits gives 81551040.

It is an unprimeable number.

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 31 ways as a sum of consecutive naturals, for example, 309949 + ... + 310211.

Almost surely, 2^81551040 is an apocalyptic number.

81551040 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 81551040, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (144840960).

81551040 is an abundant number, since it is smaller than the sum of its proper divisors (208130880).

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

81551040 is a wasteful number, since it uses less digits than its factorization.

81551040 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 319 (or 309 counting only the distinct ones).

The product of its (nonzero) digits is 800, while the sum is 24.

The square root of 81551040 is about 9030.5614443400. The cubic root of 81551040 is about 433.6538115792.

Adding to 81551040 its reverse (4015518), we get a palindrome (85566558).

The spelling of 81551040 in words is "eighty-one million, five hundred fifty-one thousand, forty".