81539984 has 10 divisors (see below), whose sum is σ = 157983750. Its totient is φ = 40769984.

The previous prime is 81539977. The next prime is 81539987. The reversal of 81539984 is 48993518.

It can be written as a sum of positive squares in only one way, i.e., 47059600 + 34480384 = 6860^2 + 5872^2 .

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81539987) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 2548109 + ... + 2548140.

It is an arithmetic number, because the mean of its divisors is an integer number (15798375).

Almost surely, 2^81539984 is an apocalyptic number.

It is an amenable number.

81539984 is a deficient number, since it is larger than the sum of its proper divisors (76443766).

81539984 is a wasteful number, since it uses less digits than its factorization.

81539984 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5096257 (or 5096251 counting only the distinct ones).

The product of its digits is 311040, while the sum is 47.

The square root of 81539984 is about 9029.9492800347. The cubic root of 81539984 is about 433.6342136553.

The spelling of 81539984 in words is "eighty-one million, five hundred thirty-nine thousand, nine hundred eighty-four".