81199540 has 96 divisors (see below), whose sum is σ = 189987840. Its totient is φ = 29030400.

The previous prime is 81199537. The next prime is 81199543. The reversal of 81199540 is 4599118.

It is an interprime number because it is at equal distance from previous prime (81199537) and next prime (81199543).

It is a self number, because there is not a number n which added to its sum of digits gives 81199540.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81199543) 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, 718524 + ... + 718636.

It is an arithmetic number, because the mean of its divisors is an integer number (1979040).

Almost surely, 2^81199540 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 81199540, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (94993920).

81199540 is an abundant number, since it is smaller than the sum of its proper divisors (108788300).

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

81199540 is a wasteful number, since it uses less digits than its factorization.

81199540 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 233 (or 231 counting only the distinct ones).

The product of its (nonzero) digits is 12960, while the sum is 37.

The square root of 81199540 is about 9011.0787367551. The cubic root of 81199540 is about 433.0298716918.

The spelling of 81199540 in words is "eighty-one million, one hundred ninety-nine thousand, five hundred forty".