81321604 has 48 divisors (see below), whose sum is σ = 176393728. Its totient is φ = 31943808.

The previous prime is 81321593. The next prime is 81321619. The reversal of 81321604 is 40612318.

It is a super-2 number, since 2×81321604² = 13226406554265632, which contains 22 as substring.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 56437 + ... + 57859.

Almost surely, 2^81321604 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 81321604, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (88196864).

81321604 is an abundant number, since it is smaller than the sum of its proper divisors (95072124).

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

81321604 is a wasteful number, since it uses less digits than its factorization.

81321604 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1604 (or 1602 counting only the distinct ones).

The product of its (nonzero) digits is 1152, while the sum is 25.

The square root of 81321604 is about 9017.8491892468. The cubic root of 81321604 is about 433.2467485125.

The spelling of 81321604 in words is "eighty-one million, three hundred twenty-one thousand, six hundred four".