1978000691 has 2 divisors, whose sum is σ = 1978000692. Its totient is φ = 1978000690.

The previous prime is 1978000631. The next prime is 1978000699. The reversal of 1978000691 is 1960008791.

It is a happy number.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 1978000691 - 2¹⁸ = 1977738547 is a prime.

It is not a weakly prime, because it can be changed into another prime (1978000699) 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, 989000345 + 989000346.

It is an arithmetic number, because the mean of its divisors is an integer number (989000346).

Almost surely, 2^1978000691 is an apocalyptic number.

1978000691 is a deficient number, since it is larger than the sum of its proper divisors (1).

1978000691 is an equidigital number, since it uses as much as digits as its factorization.

1978000691 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 27216, while the sum is 41.

The square root of 1978000691 is about 44474.7196843330. The cubic root of 1978000691 is about 1255.2844423338.

The spelling of 1978000691 in words is "one billion, nine hundred seventy-eight million, six hundred ninety-one", and thus it is an aban number.