81408240 has 200 divisors, whose sum is σ = 299779920. Its totient is φ = 20404224.

The previous prime is 81408233. The next prime is 81408253. The reversal of 81408240 is 4280418.

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

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 39 ways as a sum of consecutive naturals, for example, 109791 + ... + 110529.

Almost surely, 2^81408240 is an apocalyptic number.

81408240 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 81408240, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (149889960).

81408240 is an abundant number, since it is smaller than the sum of its proper divisors (218371680).

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

81408240 is a wasteful number, since it uses less digits than its factorization.

81408240 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 781 (or 766 counting only the distinct ones).

The product of its (nonzero) digits is 2048, while the sum is 27.

The square root of 81408240 is about 9022.6514949875. The cubic root of 81408240 is about 433.4005471020.

Adding to 81408240 its reverse (4280418), we get a palindrome (85688658).

It can be divided in two parts, 81 and 408240, that added together give a square (408321 = 639²).

The spelling of 81408240 in words is "eighty-one million, four hundred eight thousand, two hundred forty".