81520207 has 4 divisors (see below), whose sum is σ = 81555280. Its totient is φ = 81485136.

The previous prime is 81520199. The next prime is 81520223. The reversal of 81520207 is 70202518.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 70202518 = 2 ⋅35101259.

It is a cyclic number.

It is not a de Polignac number, because 81520207 - 2³ = 81520199 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 (81520237) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 13782 + ... + 18787.

It is an arithmetic number, because the mean of its divisors is an integer number (20388820).

Almost surely, 2^81520207 is an apocalyptic number.

81520207 is a deficient number, since it is larger than the sum of its proper divisors (35073).

81520207 is a wasteful number, since it uses less digits than its factorization.

81520207 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 35072.

The product of its (nonzero) digits is 1120, while the sum is 25.

The square root of 81520207 is about 9028.8541354925. The cubic root of 81520207 is about 433.5991524217.

The spelling of 81520207 in words is "eighty-one million, five hundred twenty thousand, two hundred seven".