81207517 has 2 divisors, whose sum is σ = 81207518. Its totient is φ = 81207516.

The previous prime is 81207491. The next prime is 81207559. The reversal of 81207517 is 71570218.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 74545956 + 6661561 = 8634^2 + 2581^2 .

It is a cyclic number.

It is not a de Polignac number, because 81207517 - 2⁷ = 81207389 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (81007517) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40603758 + 40603759.

It is an arithmetic number, because the mean of its divisors is an integer number (40603759).

Almost surely, 2^81207517 is an apocalyptic number.

It is an amenable number.

81207517 is a deficient number, since it is larger than the sum of its proper divisors (1).

81207517 is an equidigital number, since it uses as much as digits as its factorization.

81207517 is an evil number, because the sum of its binary digits is even.

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

The square root of 81207517 is about 9011.5213476971. The cubic root of 81207517 is about 433.0440514362.

The spelling of 81207517 in words is "eighty-one million, two hundred seven thousand, five hundred seventeen".