7821211261 has 2 divisors, whose sum is σ = 7821211262. Its totient is φ = 7821211260.

The previous prime is 7821211259. The next prime is 7821211303. The reversal of 7821211261 is 1621121287.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 4045723236 + 3775488025 = 63606^2 + 61445^2 .

It is a cyclic number.

It is not a de Polignac number, because 7821211261 - 2¹ = 7821211259 is a prime.

It is a super-2 number, since 2×7821211261² (a number of 21 digits) contains 22 as substring.

Together with 7821211259, it forms a pair of twin primes.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (7821211241) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 3910605630 + 3910605631.

It is an arithmetic number, because the mean of its divisors is an integer number (3910605631).

Almost surely, 2^7821211261 is an apocalyptic number.

It is an amenable number.

7821211261 is a deficient number, since it is larger than the sum of its proper divisors (1).

7821211261 is an equidigital number, since it uses as much as digits as its factorization.

7821211261 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 2688, while the sum is 31.

The square root of 7821211261 is about 88437.6122529323. The cubic root of 7821211261 is about 1984.9885484728.

The spelling of 7821211261 in words is "seven billion, eight hundred twenty-one million, two hundred eleven thousand, two hundred sixty-one".