81458640 has 120 divisors (see below), whose sum is σ = 285517440. Its totient is φ = 20773632.

The previous prime is 81458623. The next prime is 81458653. The reversal of 81458640 is 4685418.

81458640 is a `hidden beast` number, since 8 + 1 + 4 + 5 + 8 + 640 = 666.

It is a tau number, because it is divible by the number of its divisors (120).

It is a Harshad number since it is a multiple of its sum of digits (36).

It is a junction number, because it is equal to n+sod(n) for n = 81458595 and 81458604.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 14101 + ... + 19019.

It is an arithmetic number, because the mean of its divisors is an integer number (2379312).

Almost surely, 2^81458640 is an apocalyptic number.

81458640 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 81458640, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (142758720).

81458640 is an abundant number, since it is smaller than the sum of its proper divisors (204058800).

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

81458640 is a wasteful number, since it uses less digits than its factorization.

81458640 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4961 (or 4952 counting only the distinct ones).

The product of its (nonzero) digits is 30720, while the sum is 36.

The square root of 81458640 is about 9025.4440333980. Note that the first 3 decimals coincide. The cubic root of 81458640 is about 433.4899683586.

The spelling of 81458640 in words is "eighty-one million, four hundred fifty-eight thousand, six hundred forty".