81777280 has 64 divisors (see below), whose sum is σ = 210558600. Its totient is φ = 30191616.

The previous prime is 81777239. The next prime is 81777281. The reversal of 81777280 is 8277718.

It is a happy number.

It can be written as a sum of positive squares in 4 ways, for example, as 68293696 + 13483584 = 8264^2 + 3672^2 .

It is a tau number, because it is divible by the number of its divisors (64).

It is a Harshad number since it is a multiple of its sum of digits (40).

It is not an unprimeable number, because it can be changed into a prime (81777281) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 3406 + ... + 13234.

Almost surely, 2^81777280 is an apocalyptic number.

81777280 is a gapful number since it is divisible by the number (80) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 81777280, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (105279300).

81777280 is an abundant number, since it is smaller than the sum of its proper divisors (128781320).

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

81777280 is a wasteful number, since it uses less digits than its factorization.

81777280 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 9861 (or 9849 counting only the distinct ones).

The product of its (nonzero) digits is 43904, while the sum is 40.

The square root of 81777280 is about 9043.0791216267. The cubic root of 81777280 is about 434.0544574080.

The spelling of 81777280 in words is "eighty-one million, seven hundred seventy-seven thousand, two hundred eighty".