7821691 has 2 divisors, whose sum is σ = 7821692. Its totient is φ = 7821690.

The previous prime is 7821661. The next prime is 7821701. The reversal of 7821691 is 1961287.

It is a happy number.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 7821691 - 2⁷ = 7821563 is a prime.

It is a super-2 number, since 2×7821691² = 122357700198962, which contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (7821601) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 3910845 + 3910846.

It is an arithmetic number, because the mean of its divisors is an integer number (3910846).

Almost surely, 2^7821691 is an apocalyptic number.

7821691 is a deficient number, since it is larger than the sum of its proper divisors (1).

7821691 is an equidigital number, since it uses as much as digits as its factorization.

7821691 is an evil number, because the sum of its binary digits is even.

The product of its digits is 6048, while the sum is 34.

The square root of 7821691 is about 2796.7286246613. The cubic root of 7821691 is about 198.5029132850.

The spelling of 7821691 in words is "seven million, eight hundred twenty-one thousand, six hundred ninety-one".