3978820691 has 2 divisors, whose sum is σ = 3978820692. Its totient is φ = 3978820690.

The previous prime is 3978820679. The next prime is 3978820697. The reversal of 3978820691 is 1960288793.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 3978820691 - 2⁶ = 3978820627 is a prime.

It is a super-2 number, since 2×3978820691² = 31662028182259434962, which contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (3978820697) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 1989410345 + 1989410346.

It is an arithmetic number, because the mean of its divisors is an integer number (1989410346).

Almost surely, 2^3978820691 is an apocalyptic number.

3978820691 is a deficient number, since it is larger than the sum of its proper divisors (1).

3978820691 is an equidigital number, since it uses as much as digits as its factorization.

3978820691 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 1306368, while the sum is 53.

The square root of 3978820691 is about 63077.8938376988. The cubic root of 3978820691 is about 1584.5944211336.

The spelling of 3978820691 in words is "three billion, nine hundred seventy-eight million, eight hundred twenty thousand, six hundred ninety-one".