81157120 has 132 divisors (see below), whose sum is σ = 215622792. Its totient is φ = 29286400.

The previous prime is 81157117. The next prime is 81157121. The reversal of 81157120 is 2175118.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81157121) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 619455 + ... + 619585.

It is an arithmetic number, because the mean of its divisors is an integer number (1633506).

Almost surely, 2^81157120 is an apocalyptic number.

81157120 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 81157120, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (107811396).

81157120 is an abundant number, since it is smaller than the sum of its proper divisors (134465672).

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

81157120 is a wasteful number, since it uses less digits than its factorization.

81157120 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 178 (or 149 counting only the distinct ones).

The product of its (nonzero) digits is 560, while the sum is 25.

The square root of 81157120 is about 9008.7246600171. The cubic root of 81157120 is about 432.9544512035.

The spelling of 81157120 in words is "eighty-one million, one hundred fifty-seven thousand, one hundred twenty".