81321408 has 224 divisors, whose sum is σ = 279928320. Its totient is φ = 22954752.

The previous prime is 81321407. The next prime is 81321431. The reversal of 81321408 is 80412318.

It is a tau number, because it is divible by the number of its divisors (224).

It is a super-2 number, since 2×81321408² = 13226342798204928, which contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (27).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81321407) by changing a digit.

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 31 ways as a sum of consecutive naturals, for example, 979735 + ... + 979817.

It is an arithmetic number, because the mean of its divisors is an integer number (1249680).

Almost surely, 2^81321408 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 81321408, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (139964160).

81321408 is an abundant number, since it is smaller than the sum of its proper divisors (198606912).

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

81321408 is an frugal number, since it uses more digits than its factorization.

81321408 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 123 (or 95 counting only the distinct ones).

The product of its (nonzero) digits is 1536, while the sum is 27.

The square root of 81321408 is about 9017.8383219040. The cubic root of 81321408 is about 433.2464004442.

It can be divided in two parts, 81 and 321408, that added together give a square (321489 = 567²).

The spelling of 81321408 in words is "eighty-one million, three hundred twenty-one thousand, four hundred eight".