81802321 has 2 divisors, whose sum is σ = 81802322. Its totient is φ = 81802320.

The previous prime is 81802319. The next prime is 81802349. The reversal of 81802321 is 12320818.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 73017025 + 8785296 = 8545^2 + 2964^2 .

It is a cyclic number.

It is not a de Polignac number, because 81802321 - 2¹ = 81802319 is a prime.

Together with 81802319, it forms a pair of twin primes.

It is not a weakly prime, because it can be changed into another prime (81802361) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40901160 + 40901161.

It is an arithmetic number, because the mean of its divisors is an integer number (40901161).

Almost surely, 2^81802321 is an apocalyptic number.

It is an amenable number.

81802321 is a deficient number, since it is larger than the sum of its proper divisors (1).

81802321 is an equidigital number, since it uses as much as digits as its factorization.

81802321 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 768, while the sum is 25.

The square root of 81802321 is about 9044.4635551259. The cubic root of 81802321 is about 434.0987567881.

It can be divided in two parts, 8180 and 2321, that added together give a palindrome (10501).

The spelling of 81802321 in words is "eighty-one million, eight hundred two thousand, three hundred twenty-one".