19810139 has 2 divisors, whose sum is σ = 19810140. Its totient is φ = 19810138.

The previous prime is 19810127. The next prime is 19810159. The reversal of 19810139 is 93101891.

It is a weak prime.

It is an emirp because it is prime and its reverse (93101891) is a distict prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-19810139 is a prime.

It is a Sophie Germain prime.

It is not a weakly prime, because it can be changed into another prime (19810159) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9905069 + 9905070.

It is an arithmetic number, because the mean of its divisors is an integer number (9905070).

Almost surely, 2^19810139 is an apocalyptic number.

19810139 is a deficient number, since it is larger than the sum of its proper divisors (1).

19810139 is an equidigital number, since it uses as much as digits as its factorization.

19810139 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 1944, while the sum is 32.

The square root of 19810139 is about 4450.8582318470. The cubic root of 19810139 is about 270.5800925188.

The spelling of 19810139 in words is "nineteen million, eight hundred ten thousand, one hundred thirty-nine".