81870517 has 2 divisors, whose sum is σ = 81870518. Its totient is φ = 81870516.

The previous prime is 81870497. The next prime is 81870541. The reversal of 81870517 is 71507818.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 81830116 + 40401 = 9046^2 + 201^2 .

It is a cyclic number.

It is not a de Polignac number, because 81870517 - 2⁷ = 81870389 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (81870557) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40935258 + 40935259.

It is an arithmetic number, because the mean of its divisors is an integer number (40935259).

Almost surely, 2^81870517 is an apocalyptic number.

It is an amenable number.

81870517 is a deficient number, since it is larger than the sum of its proper divisors (1).

81870517 is an equidigital number, since it uses as much as digits as its factorization.

81870517 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 15680, while the sum is 37.

The square root of 81870517 is about 9048.2328108863. The cubic root of 81870517 is about 434.2193547356.

The spelling of 81870517 in words is "eighty-one million, eight hundred seventy thousand, five hundred seventeen".