81505999 has 2 divisors, whose sum is σ = 81506000. Its totient is φ = 81505998.

The previous prime is 81505987. The next prime is 81506053. The reversal of 81505999 is 99950518.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 81505999 - 2¹¹ = 81503951 is a prime.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (81505199) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40752999 + 40753000.

It is an arithmetic number, because the mean of its divisors is an integer number (40753000).

Almost surely, 2^81505999 is an apocalyptic number.

81505999 is a deficient number, since it is larger than the sum of its proper divisors (1).

81505999 is an equidigital number, since it uses as much as digits as its factorization.

81505999 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 145800, while the sum is 46.

The square root of 81505999 is about 9028.0672904005. The cubic root of 81505999 is about 433.5739605708.

The spelling of 81505999 in words is "eighty-one million, five hundred five thousand, nine hundred ninety-nine".