19705991 has 2 divisors, whose sum is σ = 19705992. Its totient is φ = 19705990.

The previous prime is 19705981. The next prime is 19706003. The reversal of 19705991 is 19950791.

It is a happy number.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 19705991 - 2⁶ = 19705927 is a prime.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (19705901) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9852995 + 9852996.

It is an arithmetic number, because the mean of its divisors is an integer number (9852996).

Almost surely, 2^19705991 is an apocalyptic number.

19705991 is a deficient number, since it is larger than the sum of its proper divisors (1).

19705991 is an equidigital number, since it uses as much as digits as its factorization.

19705991 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 25515, while the sum is 41.

The square root of 19705991 is about 4439.1430479317. The cubic root of 19705991 is about 270.1050848384.

The spelling of 19705991 in words is "nineteen million, seven hundred five thousand, nine hundred ninety-one".