81221584 has 10 divisors (see below), whose sum is σ = 157366850. Its totient is φ = 40610784.

The previous prime is 81221573. The next prime is 81221587. The reversal of 81221584 is 48512218.

It can be written as a sum of positive squares in only one way, i.e., 66781584 + 14440000 = 8172^2 + 3800^2 .

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81221587) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 2538159 + ... + 2538190.

It is an arithmetic number, because the mean of its divisors is an integer number (15736685).

Almost surely, 2^81221584 is an apocalyptic number.

It is an amenable number.

81221584 is a deficient number, since it is larger than the sum of its proper divisors (76145266).

81221584 is a wasteful number, since it uses less digits than its factorization.

81221584 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5076357 (or 5076351 counting only the distinct ones).

The product of its digits is 5120, while the sum is 31.

The square root of 81221584 is about 9012.3018147419. The cubic root of 81221584 is about 433.0690543719.

The spelling of 81221584 in words is "eighty-one million, two hundred twenty-one thousand, five hundred eighty-four".