81507280 has 40 divisors (see below), whose sum is σ = 189887400. Its totient is φ = 32537088.

The previous prime is 81507253. The next prime is 81507281. The reversal of 81507280 is 8270518.

It can be written as a sum of positive squares in 4 ways, for example, as 33454656 + 48052624 = 5784^2 + 6932^2 .

It is a tau number, because it is divible by the number of its divisors (40).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81507281) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 65706 + ... + 66934.

It is an arithmetic number, because the mean of its divisors is an integer number (4747185).

Almost surely, 2^81507280 is an apocalyptic number.

81507280 is a gapful number since it is divisible by the number (80) formed by its first and last digit.

It is an amenable number.

81507280 is an abundant number, since it is smaller than the sum of its proper divisors (108380120).

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

81507280 is a wasteful number, since it uses less digits than its factorization.

81507280 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2071 (or 2065 counting only the distinct ones).

The product of its (nonzero) digits is 4480, while the sum is 31.

The square root of 81507280 is about 9028.1382355389. The cubic root of 81507280 is about 433.5762320001.

Adding to 81507280 its reverse (8270518), we get a palindrome (89777798).

The spelling of 81507280 in words is "eighty-one million, five hundred seven thousand, two hundred eighty".