81821365 has 8 divisors (see below), whose sum is σ = 98272440. Its totient is φ = 65399232.

The previous prime is 81821359. The next prime is 81821371. The reversal of 81821365 is 56312818.

It is an interprime number because it is at equal distance from previous prime (81821359) and next prime (81821371).

It can be written as a sum of positive squares in 4 ways, for example, as 44635761 + 37185604 = 6681^2 + 6098^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 81821365 - 2⁷ = 81821237 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 81821365.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 430 + ... + 12799.

It is an arithmetic number, because the mean of its divisors is an integer number (12284055).

Almost surely, 2^81821365 is an apocalyptic number.

It is an amenable number.

81821365 is a deficient number, since it is larger than the sum of its proper divisors (16451075).

81821365 is a wasteful number, since it uses less digits than its factorization.

81821365 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 14471.

The product of its digits is 11520, while the sum is 34.

The square root of 81821365 is about 9045.5162926170. The cubic root of 81821365 is about 434.1324409802.

The spelling of 81821365 in words is "eighty-one million, eight hundred twenty-one thousand, three hundred sixty-five".