7821428521 has 2 divisors, whose sum is σ = 7821428522. Its totient is φ = 7821428520.

The previous prime is 7821428501. The next prime is 7821428569. The reversal of 7821428521 is 1258241287.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 7397892121 + 423536400 = 86011^2 + 20580^2 .

It is a cyclic number.

It is not a de Polignac number, because 7821428521 - 2⁷ = 7821428393 is a prime.

It is a super-2 number, since 2×7821428521² (a number of 21 digits) contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (7821428501) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 3910714260 + 3910714261.

It is an arithmetic number, because the mean of its divisors is an integer number (3910714261).

Almost surely, 2^7821428521 is an apocalyptic number.

It is an amenable number.

7821428521 is a deficient number, since it is larger than the sum of its proper divisors (1).

7821428521 is an equidigital number, since it uses as much as digits as its factorization.

7821428521 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 71680, while the sum is 40.

The square root of 7821428521 is about 88438.8405679315. The cubic root of 7821428521 is about 1985.0069281758.

The spelling of 7821428521 in words is "seven billion, eight hundred twenty-one million, four hundred twenty-eight thousand, five hundred twenty-one".