81705487 has 2 divisors, whose sum is σ = 81705488. Its totient is φ = 81705486.

The previous prime is 81705479. The next prime is 81705511. The reversal of 81705487 is 78450718.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 81705487 - 2³ = 81705479 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (81705427) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40852743 + 40852744.

It is an arithmetic number, because the mean of its divisors is an integer number (40852744).

Almost surely, 2^81705487 is an apocalyptic number.

81705487 is a deficient number, since it is larger than the sum of its proper divisors (1).

81705487 is an equidigital number, since it uses as much as digits as its factorization.

81705487 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 62720, while the sum is 40.

The square root of 81705487 is about 9039.1087503138. The cubic root of 81705487 is about 433.9274001322.

The spelling of 81705487 in words is "eighty-one million, seven hundred five thousand, four hundred eighty-seven".