81820397 has 4 divisors (see below), whose sum is σ = 84641820. Its totient is φ = 78998976.

The previous prime is 81820369. The next prime is 81820399. The reversal of 81820397 is 79302818.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 17355556 + 64464841 = 4166^2 + 8029^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-81820397 is a prime.

It is a super-3 number, since 3×81820397³ (a number of 25 digits) contains 333 as substring.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 81820397.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81820399) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1410668 + ... + 1410725.

It is an arithmetic number, because the mean of its divisors is an integer number (21160455).

Almost surely, 2^81820397 is an apocalyptic number.

It is an amenable number.

81820397 is a deficient number, since it is larger than the sum of its proper divisors (2821423).

81820397 is a wasteful number, since it uses less digits than its factorization.

81820397 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2821422.

The product of its (nonzero) digits is 24192, while the sum is 38.

The square root of 81820397 is about 9045.4627852863. The cubic root of 81820397 is about 434.1307289503.

The spelling of 81820397 in words is "eighty-one million, eight hundred twenty thousand, three hundred ninety-seven".