71821681 has 4 divisors (see below), whose sum is σ = 71861364. Its totient is φ = 71782000.

The previous prime is 71821679. The next prime is 71821693. The reversal of 71821681 is 18612817.

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 31181056 + 40640625 = 5584^2 + 6375^2 .

It is a cyclic number.

It is not a de Polignac number, because 71821681 - 2¹ = 71821679 is a prime.

It is a super-2 number, since 2×71821681² = 10316707723331522, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (71821601) 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, 16990 + ... + 20791.

It is an arithmetic number, because the mean of its divisors is an integer number (17965341).

Almost surely, 2^71821681 is an apocalyptic number.

It is an amenable number.

71821681 is a deficient number, since it is larger than the sum of its proper divisors (39683).

71821681 is a wasteful number, since it uses less digits than its factorization.

71821681 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 39682.

The product of its digits is 5376, while the sum is 34.

The square root of 71821681 is about 8474.7673124399. The cubic root of 71821681 is about 415.6730376647.

The spelling of 71821681 in words is "seventy-one million, eight hundred twenty-one thousand, six hundred eighty-one".