81501665 has 8 divisors (see below), whose sum is σ = 111773760. Its totient is φ = 55886832.

The previous prime is 81501643. The next prime is 81501671. The reversal of 81501665 is 56610518.

It is a happy number.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 81501665 - 2¹⁰ = 81500641 is a prime.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 1164275 + ... + 1164344.

It is an arithmetic number, because the mean of its divisors is an integer number (13971720).

Almost surely, 2^81501665 is an apocalyptic number.

It is an amenable number.

81501665 is a deficient number, since it is larger than the sum of its proper divisors (30272095).

81501665 is a wasteful number, since it uses less digits than its factorization.

81501665 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2328631.

The product of its (nonzero) digits is 7200, while the sum is 32.

The square root of 81501665 is about 9027.8272579841. The cubic root of 81501665 is about 433.5662754807.

The spelling of 81501665 in words is "eighty-one million, five hundred one thousand, six hundred sixty-five".