81500236991 has 8 divisors (see below), whose sum is σ = 82935404160. Its totient is φ = 80066863512.

The previous prime is 81500236963. The next prime is 81500237023. The reversal of 81500236991 is 19963200518.

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 81500236991 - 2¹⁸ = 81499974847 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81500236291) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 356585 + ... + 538658.

It is an arithmetic number, because the mean of its divisors is an integer number (10366925520).

Almost surely, 2^81500236991 is an apocalyptic number.

81500236991 is a deficient number, since it is larger than the sum of its proper divisors (1435167169).

81500236991 is a wasteful number, since it uses less digits than its factorization.

81500236991 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 896845.

The product of its (nonzero) digits is 116640, while the sum is 44.

The spelling of 81500236991 in words is "eighty-one billion, five hundred million, two hundred thirty-six thousand, nine hundred ninety-one".