81501817 has 4 divisors (see below), whose sum is σ = 81867520. Its totient is φ = 81136116.

The previous prime is 81501779. The next prime is 81501881. The reversal of 81501817 is 71810518.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 81501817 - 2¹⁹ = 80977529 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (81501517) by changing a digit.

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 3 ways as a sum of consecutive naturals, for example, 182517 + ... + 182962.

It is an arithmetic number, because the mean of its divisors is an integer number (20466880).

Almost surely, 2^81501817 is an apocalyptic number.

It is an amenable number.

81501817 is a deficient number, since it is larger than the sum of its proper divisors (365703).

81501817 is a wasteful number, since it uses less digits than its factorization.

81501817 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 365702.

The product of its (nonzero) digits is 2240, while the sum is 31.

The square root of 81501817 is about 9027.8356763955. The cubic root of 81501817 is about 433.5665450131.

The spelling of 81501817 in words is "eighty-one million, five hundred one thousand, eight hundred seventeen".