81501868449 has 12 divisors (see below), whose sum is σ = 118766736036. Its totient is φ = 53853741312.

The previous prime is 81501868439. The next prime is 81501868471. The reversal of 81501868449 is 94486810518.

It is a happy number.

81501868449 is a `hidden beast` number, since 8 + 15 + 0 + 186 + 8 + 449 = 666.

It can be written as a sum of positive squares in 2 ways, for example, as 1308124224 + 80193744225 = 36168^2 + 283185^2 .

It is not a de Polignac number, because 81501868449 - 2⁴ = 81501868433 is a prime.

It is a Curzon number.

It is a junction number, because it is equal to n+sod(n) for n = 81501868395 and 81501868404.

It is not an unprimeable number, because it can be changed into a prime (81501868439) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 40068732 + ... + 40070765.

It is an arithmetic number, because the mean of its divisors is an integer number (9897228003).

Almost surely, 2^81501868449 is an apocalyptic number.

It is an amenable number.

81501868449 is a deficient number, since it is larger than the sum of its proper divisors (37264867587).

81501868449 is a wasteful number, since it uses less digits than its factorization.

81501868449 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 80139616 (or 80139613 counting only the distinct ones).

The product of its (nonzero) digits is 2211840, while the sum is 54.

The spelling of 81501868449 in words is "eighty-one billion, five hundred one million, eight hundred sixty-eight thousand, four hundred forty-nine".