81235440 has 320 divisors, whose sum is σ = 329978880. Its totient is φ = 18109440.

The previous prime is 81235439. The next prime is 81235447. The reversal of 81235440 is 4453218.

It is a hoax number, since the sum of its digits (27) coincides with the sum of the digits of its distinct prime factors.

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 (81235447) by changing a digit.

It is a polite number, since it can be written in 63 ways as a sum of consecutive naturals, for example, 308749 + ... + 309011.

It is an arithmetic number, because the mean of its divisors is an integer number (1031184).

Almost surely, 2^81235440 is an apocalyptic number.

81235440 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 81235440, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (164989440).

81235440 is an abundant number, since it is smaller than the sum of its proper divisors (248743440).

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

81235440 is a wasteful number, since it uses less digits than its factorization.

81235440 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 309 (or 297 counting only the distinct ones).

The product of its (nonzero) digits is 3840, while the sum is 27.

The square root of 81235440 is about 9013.0705089886. The cubic root of 81235440 is about 433.0936794503.

Adding to 81235440 its reverse (4453218), we get a palindrome (85688658).

The spelling of 81235440 in words is "eighty-one million, two hundred thirty-five thousand, four hundred forty".