19873991 has 2 divisors, whose sum is σ = 19873992. Its totient is φ = 19873990.

The previous prime is 19873963. The next prime is 19874011. The reversal of 19873991 is 19937891.

It is a happy number.

It is a strong prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-19873991 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 (19873291) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9936995 + 9936996.

It is an arithmetic number, because the mean of its divisors is an integer number (9936996).

Almost surely, 2^19873991 is an apocalyptic number.

19873991 is a deficient number, since it is larger than the sum of its proper divisors (1).

19873991 is an equidigital number, since it uses as much as digits as its factorization.

19873991 is an evil number, because the sum of its binary digits is even.

The product of its digits is 122472, while the sum is 47.

The square root of 19873991 is about 4458.0254597748. The cubic root of 19873991 is about 270.8704918063.

The spelling of 19873991 in words is "nineteen million, eight hundred seventy-three thousand, nine hundred ninety-one".