81007780 has 72 divisors (see below), whose sum is σ = 199717056. Its totient is φ = 27518400.

The previous prime is 81007777. The next prime is 81007793. The reversal of 81007780 is 8770018.

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, 128065 + ... + 128695.

It is an arithmetic number, because the mean of its divisors is an integer number (2773848).

Almost surely, 2^81007780 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 81007780, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (99858528).

81007780 is an abundant number, since it is smaller than the sum of its proper divisors (118709276).

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

81007780 is a wasteful number, since it uses less digits than its factorization.

81007780 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 785 (or 776 counting only the distinct ones).

The product of its (nonzero) digits is 3136, while the sum is 31.

The square root of 81007780 is about 9000.4322118441. The cubic root of 81007780 is about 432.6887233668.

Adding to 81007780 its reverse (8770018), we get a palindrome (89777798).

The spelling of 81007780 in words is "eighty-one million, seven thousand, seven hundred eighty".