81361280 has 256 divisors, whose sum is σ = 263208960. Its totient is φ = 23224320.

The previous prime is 81361279. The next prime is 81361297. The reversal of 81361280 is 8216318.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 640577 + ... + 640703.

It is an arithmetic number, because the mean of its divisors is an integer number (1028160).

Almost surely, 2^81361280 is an apocalyptic number.

81361280 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 81361280, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (131604480).

81361280 is an abundant number, since it is smaller than the sum of its proper divisors (181847680).

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

81361280 is a wasteful number, since it uses less digits than its factorization.

81361280 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 177 (or 165 counting only the distinct ones).

The product of its (nonzero) digits is 2304, while the sum is 29.

The square root of 81361280 is about 9020.0487803559. The cubic root of 81361280 is about 433.3171959802.

Adding to 81361280 its reverse (8216318), we get a palindrome (89577598).

The spelling of 81361280 in words is "eighty-one million, three hundred sixty-one thousand, two hundred eighty".