81539280 has 120 divisors (see below), whose sum is σ = 275506920. Its totient is φ = 21611520.

The previous prime is 81539273. The next prime is 81539291. The reversal of 81539280 is 8293518.

It can be written as a sum of positive squares in 4 ways, for example, as 7096896 + 74442384 = 2664^2 + 8628^2 .

It is a tau number, because it is divible by the number of its divisors (120).

It is a Harshad number since it is a multiple of its sum of digits (36).

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 193470 + ... + 193890.

It is an arithmetic number, because the mean of its divisors is an integer number (2295891).

Almost surely, 2^81539280 is an apocalyptic number.

81539280 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 81539280, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (137753460).

81539280 is an abundant number, since it is smaller than the sum of its proper divisors (193967640).

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

81539280 is a wasteful number, since it uses less digits than its factorization.

81539280 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 709 (or 700 counting only the distinct ones).

The product of its (nonzero) digits is 17280, while the sum is 36.

The square root of 81539280 is about 9029.9102985578. The cubic root of 81539280 is about 433.6329656812.

The spelling of 81539280 in words is "eighty-one million, five hundred thirty-nine thousand, two hundred eighty".