81517207 has 4 divisors (see below), whose sum is σ = 83413000. Its totient is φ = 79621416.

The previous prime is 81517171. The next prime is 81517211. The reversal of 81517207 is 70271518.

It is a happy number.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 70271518 = 2 ⋅35135759.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-81517207 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 (81517237) 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, 947832 + ... + 947917.

It is an arithmetic number, because the mean of its divisors is an integer number (20853250).

Almost surely, 2^81517207 is an apocalyptic number.

81517207 is a deficient number, since it is larger than the sum of its proper divisors (1895793).

81517207 is a wasteful number, since it uses less digits than its factorization.

81517207 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1895792.

The product of its (nonzero) digits is 3920, while the sum is 31.

The square root of 81517207 is about 9028.6879999256. The cubic root of 81517207 is about 433.5938334402.

The spelling of 81517207 in words is "eighty-one million, five hundred seventeen thousand, two hundred seven".