81651587065 has 16 divisors (see below), whose sum is σ = 99131760000. Its totient is φ = 64557245952.

The previous prime is 81651587029. The next prime is 81651587077. The reversal of 81651587065 is 56078515618.

It is a happy number.

It is a cyclic number.

It is not a de Polignac number, because 81651587065 - 2¹⁷ = 81651455993 is a prime.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 98121 + ... + 415849.

It is an arithmetic number, because the mean of its divisors is an integer number (6195735000).

Almost surely, 2^81651587065 is an apocalyptic number.

It is an amenable number.

81651587065 is a deficient number, since it is larger than the sum of its proper divisors (17480172935).

81651587065 is a wasteful number, since it uses less digits than its factorization.

81651587065 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 318336.

The product of its (nonzero) digits is 2016000, while the sum is 52.

The spelling of 81651587065 in words is "eighty-one billion, six hundred fifty-one million, five hundred eighty-seven thousand, sixty-five".