6821787121 has 2 divisors, whose sum is σ = 6821787122. Its totient is φ = 6821787120.

The previous prime is 6821787109. The next prime is 6821787209. The reversal of 6821787121 is 1217871286.

6821787121 is digitally balanced in base 3, because in such base it contains all the possibile digits an equal number of times.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 4420787121 + 2401000000 = 66489^2 + 49000^2 .

It is a cyclic number.

It is not a de Polignac number, because 6821787121 - 2¹⁵ = 6821754353 is a prime.

It is not a weakly prime, because it can be changed into another prime (6821787101) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 3410893560 + 3410893561.

It is an arithmetic number, because the mean of its divisors is an integer number (3410893561).

Almost surely, 2^6821787121 is an apocalyptic number.

It is an amenable number.

6821787121 is a deficient number, since it is larger than the sum of its proper divisors (1).

6821787121 is an equidigital number, since it uses as much as digits as its factorization.

6821787121 is an evil number, because the sum of its binary digits is even.

The product of its digits is 75264, while the sum is 43.

The square root of 6821787121 is about 82594.1106919858. The cubic root of 6821787121 is about 1896.5576748899.

The spelling of 6821787121 in words is "six billion, eight hundred twenty-one million, seven hundred eighty-seven thousand, one hundred twenty-one".