81329280 has 64 divisors (see below), whose sum is σ = 259243200. Its totient is φ = 21687296.

The previous prime is 81329263. The next prime is 81329323. The reversal of 81329280 is 8292318.

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

It is a super-2 number, since 2×81329280² = 13228903570636800, which contains 22 as substring.

It is a hoax number, since the sum of its digits (33) coincides with the sum of the digits of its distinct prime factors.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 19260 + ... + 23099.

It is an arithmetic number, because the mean of its divisors is an integer number (4050675).

Almost surely, 2^81329280 is an apocalyptic number.

81329280 is a gapful number since it is divisible by the number (80) formed by its first and last digit.

It is an amenable number.

81329280 is an abundant number, since it is smaller than the sum of its proper divisors (177913920).

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

81329280 is a wasteful number, since it uses less digits than its factorization.

81329280 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 42381 (or 42369 counting only the distinct ones).

The product of its (nonzero) digits is 6912, while the sum is 33.

The square root of 81329280 is about 9018.2747795795. The cubic root of 81329280 is about 433.2603795660.

The spelling of 81329280 in words is "eighty-one million, three hundred twenty-nine thousand, two hundred eighty".