81913440 has 96 divisors (see below), whose sum is σ = 294900480. Its totient is φ = 18722304.

The previous prime is 81913421. The next prime is 81913451. The reversal of 81913440 is 4431918.

It is a happy number.

It is a tau number, because it is divible by the number of its divisors (96).

It is a Harshad number since it is a multiple of its sum of digits (30).

It is a junction number, because it is equal to n+sod(n) for n = 81913398 and 81913407.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 8830 + ... + 15549.

It is an arithmetic number, because the mean of its divisors is an integer number (3071880).

Almost surely, 2^81913440 is an apocalyptic number.

81913440 is a gapful number since it is divisible by the number (80) formed by its first and last digit.

It is an amenable number.

81913440 is an abundant number, since it is smaller than the sum of its proper divisors (212987040).

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

81913440 is a wasteful number, since it uses less digits than its factorization.

81913440 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 24404 (or 24396 counting only the distinct ones).

The product of its (nonzero) digits is 3456, while the sum is 30.

The square root of 81913440 is about 9050.6043997072. The cubic root of 81913440 is about 434.2952255205.

The spelling of 81913440 in words is "eighty-one million, nine hundred thirteen thousand, four hundred forty".