82721381 has 8 divisors (see below), whose sum is σ = 85089144. Its totient is φ = 80360640.

The previous prime is 82721357. The next prime is 82721389. The reversal of 82721381 is 18312728.

It can be written as a sum of positive squares in 4 ways, for example, as 20784481 + 61936900 = 4559^2 + 7870^2 .

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

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-82721381 is a prime.

It is a super-2 number, since 2×82721381² = 13685653749094322, which contains 22 as substring.

It is a Duffinian number.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (82721389) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 30251 + ... + 32871.

It is an arithmetic number, because the mean of its divisors is an integer number (10636143).

Almost surely, 2^82721381 is an apocalyptic number.

It is an amenable number.

82721381 is a deficient number, since it is larger than the sum of its proper divisors (2367763).

82721381 is a wasteful number, since it uses less digits than its factorization.

82721381 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3511.

The product of its digits is 5376, while the sum is 32.

The square root of 82721381 is about 9095.1295207930. The cubic root of 82721381 is about 435.7184252841.

The spelling of 82721381 in words is "eighty-two million, seven hundred twenty-one thousand, three hundred eighty-one".