6421031521 has 2 divisors, whose sum is σ = 6421031522. Its totient is φ = 6421031520.

The previous prime is 6421031501. The next prime is 6421031579. The reversal of 6421031521 is 1251301246.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 6320250000 + 100781521 = 79500^2 + 10039^2 .

It is a cyclic number.

It is not a de Polignac number, because 6421031521 - 2⁵ = 6421031489 is a prime.

It is not a weakly prime, because it can be changed into another prime (6421031501) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 3210515760 + 3210515761.

It is an arithmetic number, because the mean of its divisors is an integer number (3210515761).

Almost surely, 2^6421031521 is an apocalyptic number.

It is an amenable number.

6421031521 is a deficient number, since it is larger than the sum of its proper divisors (1).

6421031521 is an equidigital number, since it uses as much as digits as its factorization.

6421031521 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 1440, while the sum is 25.

The square root of 6421031521 is about 80131.3391938510. The cubic root of 6421031521 is about 1858.6670529459.

Adding to 6421031521 its reverse (1251301246), we get a palindrome (7672332767).

The spelling of 6421031521 in words is "six billion, four hundred twenty-one million, thirty-one thousand, five hundred twenty-one".