7821634021 has 4 divisors (see below), whose sum is σ = 7899076044. Its totient is φ = 7744192000.

The previous prime is 7821634019. The next prime is 7821634063. The reversal of 7821634021 is 1204361287.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 1204361287 = 157 ⋅7671091.

It can be written as a sum of positive squares in 2 ways, for example, as 5899776100 + 1921857921 = 76810^2 + 43839^2 .

It is a cyclic number.

It is not a de Polignac number, because 7821634021 - 2¹ = 7821634019 is a prime.

It is a super-2 number, since 2×7821634021² (a number of 21 digits) contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (7821635021) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 38720860 + ... + 38721061.

It is an arithmetic number, because the mean of its divisors is an integer number (1974769011).

Almost surely, 2^7821634021 is an apocalyptic number.

It is an amenable number.

7821634021 is a deficient number, since it is larger than the sum of its proper divisors (77442023).

7821634021 is a wasteful number, since it uses less digits than its factorization.

7821634021 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 77442022.

The product of its (nonzero) digits is 16128, while the sum is 34.

The square root of 7821634021 is about 88440.0023801447. The cubic root of 7821634021 is about 1985.0243126962.

The spelling of 7821634021 in words is "seven billion, eight hundred twenty-one million, six hundred thirty-four thousand, twenty-one".