19856001691 has 2 divisors, whose sum is σ = 19856001692. Its totient is φ = 19856001690.

The previous prime is 19856001569. The next prime is 19856001701. The reversal of 19856001691 is 19610065891.

It is a happy number.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 19856001691 - 2²³ = 19847613083 is a prime.

It is not a weakly prime, because it can be changed into another prime (19856001391) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9928000845 + 9928000846.

It is an arithmetic number, because the mean of its divisors is an integer number (9928000846).

Almost surely, 2^19856001691 is an apocalyptic number.

19856001691 is a deficient number, since it is larger than the sum of its proper divisors (1).

19856001691 is an equidigital number, since it uses as much as digits as its factorization.

19856001691 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 116640, while the sum is 46.

The spelling of 19856001691 in words is "nineteen billion, eight hundred fifty-six million, one thousand, six hundred ninety-one".