81641280 has 112 divisors (see below), whose sum is σ = 296265600. Its totient is φ = 18659328.

The previous prime is 81641251. The next prime is 81641281. The reversal of 81641280 is 8214618.

It is a tau number, because it is divible by the number of its divisors (112).

It is a Harshad number since it is a multiple of its sum of digits (30).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81641281) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 646 + ... + 12794.

Almost surely, 2^81641280 is an apocalyptic number.

81641280 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 81641280, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (148132800).

81641280 is an abundant number, since it is smaller than the sum of its proper divisors (214624320).

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

81641280 is a wasteful number, since it uses less digits than its factorization.

81641280 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 12176 (or 12166 counting only the distinct ones).

The product of its (nonzero) digits is 3072, while the sum is 30.

The square root of 81641280 is about 9035.5564300158. The cubic root of 81641280 is about 433.8137052879.

Adding to 81641280 its reverse (8214618), we get a palindrome (89855898).

The spelling of 81641280 in words is "eighty-one million, six hundred forty-one thousand, two hundred eighty".