81217408 has 16 divisors (see below), whose sum is σ = 161800560. Its totient is φ = 40608640.

The previous prime is 81217403. The next prime is 81217417. The reversal of 81217408 is 80471218.

It is a tau number, because it is divible by the number of its divisors (16).

It is a self number, because there is not a number n which added to its sum of digits gives 81217408.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81217403) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 317128 + ... + 317383.

It is an arithmetic number, because the mean of its divisors is an integer number (10112535).

Almost surely, 2^81217408 is an apocalyptic number.

It is an amenable number.

81217408 is a deficient number, since it is larger than the sum of its proper divisors (80583152).

81217408 is an equidigital number, since it uses as much as digits as its factorization.

81217408 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 634525 (or 634513 counting only the distinct ones).

The product of its (nonzero) digits is 3584, while the sum is 31.

The square root of 81217408 is about 9012.0701284444. The cubic root of 81217408 is about 433.0616321766.

The spelling of 81217408 in words is "eighty-one million, two hundred seventeen thousand, four hundred eight".