81768915 has 12 divisors (see below), whose sum is σ = 141732864. Its totient is φ = 43610064.

The previous prime is 81768847. The next prime is 81768923. The reversal of 81768915 is 51986718.

It is not a de Polignac number, because 81768915 - 2⁹ = 81768403 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (45), and also a Moran number because the ratio is a prime number: 1817087 = 81768915 / (8 + 1 + 7 + 6 + 8 + 9 + 1 + 5).

It is an unprimeable number.

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 11 ways as a sum of consecutive naturals, for example, 908499 + ... + 908588.

It is an arithmetic number, because the mean of its divisors is an integer number (11811072).

Almost surely, 2^81768915 is an apocalyptic number.

81768915 is a deficient number, since it is larger than the sum of its proper divisors (59963949).

81768915 is a wasteful number, since it uses less digits than its factorization.

81768915 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1817098 (or 1817095 counting only the distinct ones).

The product of its digits is 120960, while the sum is 45.

The square root of 81768915 is about 9042.6166014047. The cubic root of 81768915 is about 434.0396570896.

The spelling of 81768915 in words is "eighty-one million, seven hundred sixty-eight thousand, nine hundred fifteen".