7812821 has 2 divisors, whose sum is σ = 7812822. Its totient is φ = 7812820.

The previous prime is 7812797. The next prime is 7812829. The reversal of 7812821 is 1282187.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 7022500 + 790321 = 2650^2 + 889^2 .

It is an emirp because it is prime and its reverse (1282187) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 7812821 - 2¹⁸ = 7550677 is a prime.

It is a super-2 number, since 2×7812821² = 122080343956082, which contains 22 as substring.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (7812829) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 3906410 + 3906411.

It is an arithmetic number, because the mean of its divisors is an integer number (3906411).

Almost surely, 2^7812821 is an apocalyptic number.

It is an amenable number.

7812821 is a deficient number, since it is larger than the sum of its proper divisors (1).

7812821 is an equidigital number, since it uses as much as digits as its factorization.

7812821 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 1792, while the sum is 29.

The square root of 7812821 is about 2795.1423935106. The cubic root of 7812821 is about 198.4278490894.

The spelling of 7812821 in words is "seven million, eight hundred twelve thousand, eight hundred twenty-one".