81307660 has 72 divisors (see below), whose sum is σ = 200234160. Its totient is φ = 27651456.

The previous prime is 81307657. The next prime is 81307679. The reversal of 81307660 is 6670318.

It is a super-2 number, since 2×81307660² = 13221871149351200, which contains 22 as substring.

It is an unprimeable number.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 159486 + ... + 159994.

It is an arithmetic number, because the mean of its divisors is an integer number (2781030).

Almost surely, 2^81307660 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 81307660, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (100117080).

81307660 is an abundant number, since it is smaller than the sum of its proper divisors (118926500).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

81307660 is a wasteful number, since it uses less digits than its factorization.

81307660 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 695 (or 686 counting only the distinct ones).

The product of its (nonzero) digits is 6048, while the sum is 31.

The square root of 81307660 is about 9017.0760227471. The cubic root of 81307660 is about 433.2219845396.

Adding to 81307660 its reverse (6670318), we get a palindrome (87977978).

The spelling of 81307660 in words is "eighty-one million, three hundred seven thousand, six hundred sixty".