81528199 has 4 divisors (see below), whose sum is σ = 82028536. Its totient is φ = 81027864.

The previous prime is 81528179. The next prime is 81528203. The reversal of 81528199 is 99182518.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 99182518 = 2 ⋅49591259.

It is a cyclic number.

It is not a de Polignac number, because 81528199 - 2¹⁹ = 81003911 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81528119) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 249924 + ... + 250249.

It is an arithmetic number, because the mean of its divisors is an integer number (20507134).

Almost surely, 2^81528199 is an apocalyptic number.

81528199 is a deficient number, since it is larger than the sum of its proper divisors (500337).

81528199 is a wasteful number, since it uses less digits than its factorization.

81528199 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 500336.

The product of its digits is 51840, while the sum is 43.

The square root of 81528199 is about 9029.2967057241. The cubic root of 81528199 is about 433.6133215515.

The spelling of 81528199 in words is "eighty-one million, five hundred twenty-eight thousand, one hundred ninety-nine".