821078681 has 4 divisors (see below), whose sum is σ = 821219364. Its totient is φ = 820938000.

The previous prime is 821078659. The next prime is 821078683. The reversal of 821078681 is 186870128.

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 700078681 + 121000000 = 26459^2 + 11000^2 .

It is a cyclic number.

It is not a de Polignac number, because 821078681 - 2¹⁰ = 821077657 is a prime.

It is a super-2 number, since 2×821078681² = 1348340400785399522, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (821078683) 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, 61190 + ... + 73391.

It is an arithmetic number, because the mean of its divisors is an integer number (205304841).

Almost surely, 2^821078681 is an apocalyptic number.

It is an amenable number.

821078681 is a deficient number, since it is larger than the sum of its proper divisors (140683).

821078681 is a wasteful number, since it uses less digits than its factorization.

821078681 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 140682.

The product of its (nonzero) digits is 43008, while the sum is 41.

The square root of 821078681 is about 28654.4705238118. The cubic root of 821078681 is about 936.4004031330.

The spelling of 821078681 in words is "eight hundred twenty-one million, seventy-eight thousand, six hundred eighty-one".