81517280 has 48 divisors (see below), whose sum is σ = 207404064. Its totient is φ = 30097920.

The previous prime is 81517279. The next prime is 81517283. The reversal of 81517280 is 8271518.

It is a happy number.

It is a Harshad number since it is a multiple of its sum of digits (32).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81517283) 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, 17516 + ... + 21675.

It is an arithmetic number, because the mean of its divisors is an integer number (4320918).

Almost surely, 2^81517280 is an apocalyptic number.

81517280 is a gapful number since it is divisible by the number (80) formed by its first and last digit.

It is an amenable number.

81517280 is an abundant number, since it is smaller than the sum of its proper divisors (125886784).

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

81517280 is a wasteful number, since it uses less digits than its factorization.

81517280 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 39219 (or 39211 counting only the distinct ones).

The product of its (nonzero) digits is 4480, while the sum is 32.

The square root of 81517280 is about 9028.6920425940. The cubic root of 81517280 is about 433.5939628703.

Adding to 81517280 its reverse (8271518), we get a palindrome (89788798).

The spelling of 81517280 in words is "eighty-one million, five hundred seventeen thousand, two hundred eighty".