81619440 has 160 divisors (see below), whose sum is σ = 304504320. Its totient is φ = 17667072.

The previous prime is 81619429. The next prime is 81619441. The reversal of 81619440 is 4491618.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81619441) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 30642 + ... + 33198.

It is an arithmetic number, because the mean of its divisors is an integer number (1903152).

Almost surely, 2^81619440 is an apocalyptic number.

81619440 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 81619440, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (152252160).

81619440 is an abundant number, since it is smaller than the sum of its proper divisors (222884880).

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

81619440 is a wasteful number, since it uses less digits than its factorization.

81619440 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2599 (or 2593 counting only the distinct ones).

The product of its (nonzero) digits is 6912, while the sum is 33.

The square root of 81619440 is about 9034.3477905159. The cubic root of 81619440 is about 433.7750184198.

The spelling of 81619440 in words is "eighty-one million, six hundred nineteen thousand, four hundred forty".