81908224 has 20 divisors (see below), whose sum is σ = 163657494. Its totient is φ = 40953856.

The previous prime is 81908207. The next prime is 81908243. The reversal of 81908224 is 42280918.

It can be written as a sum of positive squares in only one way, i.e., 81721600 + 186624 = 9040^2 + 432^2 .

It is a self number, because there is not a number n which added to its sum of digits gives 81908224.

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 79477 + ... + 80500.

Almost surely, 2^81908224 is an apocalyptic number.

It is an amenable number.

81908224 is a deficient number, since it is larger than the sum of its proper divisors (81749270).

81908224 is an equidigital number, since it uses as much as digits as its factorization.

81908224 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 159995 (or 159979 counting only the distinct ones).

The product of its (nonzero) digits is 9216, while the sum is 34.

The square root of 81908224 is about 9050.3162375687. The cubic root of 81908224 is about 434.2860071229.

The spelling of 81908224 in words is "eighty-one million, nine hundred eight thousand, two hundred twenty-four".