81642240 has 216 divisors, whose sum is σ = 298137840. Its totient is φ = 20570112.

The previous prime is 81642233. The next prime is 81642241. The reversal of 81642240 is 4224618.

It is not an unprimeable number, because it can be changed into a prime (81642241) 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 23 ways as a sum of consecutive naturals, for example, 218694 + ... + 219066.

Almost surely, 2^81642240 is an apocalyptic number.

81642240 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 81642240, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (149068920).

81642240 is an abundant number, since it is smaller than the sum of its proper divisors (216495600).

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

81642240 is a wasteful number, since it uses less digits than its factorization.

81642240 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 419 (or 402 counting only the distinct ones).

The product of its (nonzero) digits is 3072, while the sum is 27.

The square root of 81642240 is about 9035.6095533174. The cubic root of 81642240 is about 433.8154056513.

Adding to 81642240 its reverse (4224618), we get a palindrome (85866858).

It can be divided in two parts, 8164 and 2240, that added together give a square (10404 = 102²).

The spelling of 81642240 in words is "eighty-one million, six hundred forty-two thousand, two hundred forty".