19690991 has 2 divisors, whose sum is σ = 19690992. Its totient is φ = 19690990.

The previous prime is 19690961. The next prime is 19690997. The reversal of 19690991 is 19909691.

It is a happy number.

It is a strong prime.

It is an emirp because it is prime and its reverse (19909691) is a distict prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-19690991 is a prime.

It is a Sophie Germain prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (19690997) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9845495 + 9845496.

It is an arithmetic number, because the mean of its divisors is an integer number (9845496).

Almost surely, 2^19690991 is an apocalyptic number.

19690991 is a deficient number, since it is larger than the sum of its proper divisors (1).

19690991 is an equidigital number, since it uses as much as digits as its factorization.

19690991 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 39366, while the sum is 44.

The square root of 19690991 is about 4437.4532110209. The cubic root of 19690991 is about 270.0365336938.

The spelling of 19690991 in words is "nineteen million, six hundred ninety thousand, nine hundred ninety-one".