81437440 has 144 divisors (see below), whose sum is σ = 228110400. Its totient is φ = 27279360.

The previous prime is 81437437. The next prime is 81437443. The reversal of 81437440 is 4473418.

It is an interprime number because it is at equal distance from previous prime (81437437) and next prime (81437443).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81437443) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 546486 + ... + 546634.

It is an arithmetic number, because the mean of its divisors is an integer number (1584100).

Almost surely, 2^81437440 is an apocalyptic number.

81437440 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 81437440, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (114055200).

81437440 is an abundant number, since it is smaller than the sum of its proper divisors (146672960).

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

81437440 is a wasteful number, since it uses less digits than its factorization.

81437440 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 238 (or 224 counting only the distinct ones).

The product of its (nonzero) digits is 10752, while the sum is 31.

The square root of 81437440 is about 9024.2694995218. The cubic root of 81437440 is about 433.4523591511.

The spelling of 81437440 in words is "eighty-one million, four hundred thirty-seven thousand, four hundred forty".