19810001 has 2 divisors, whose sum is σ = 19810002. Its totient is φ = 19810000.

The previous prime is 19809991. The next prime is 19810009. The reversal of 19810001 is 10001891.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 18696976 + 1113025 = 4324^2 + 1055^2 .

It is an emirp because it is prime and its reverse (10001891) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 19810001 - 2¹⁰ = 19808977 is a prime.

It is a super-2 number, since 2×19810001² = 784872279240002, which contains 22 as substring.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (19810009) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9905000 + 9905001.

It is an arithmetic number, because the mean of its divisors is an integer number (9905001).

Almost surely, 2^19810001 is an apocalyptic number.

It is an amenable number.

19810001 is a deficient number, since it is larger than the sum of its proper divisors (1).

19810001 is an equidigital number, since it uses as much as digits as its factorization.

19810001 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 72, while the sum is 20.

The square root of 19810001 is about 4450.8427291919. The cubic root of 19810001 is about 270.5794642186.

Adding to 19810001 its reverse (10001891), we get a palindrome (29811892).

The spelling of 19810001 in words is "nineteen million, eight hundred ten thousand, one".