19990001 has 4 divisors (see below), whose sum is σ = 20477604. Its totient is φ = 19502400.

The previous prime is 19989997. The next prime is 19990031. The reversal of 19990001 is 10009991.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 6477025 + 13512976 = 2545^2 + 3676^2 .

It is a cyclic number.

It is not a de Polignac number, because 19990001 - 2² = 19989997 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (19990031) 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 in 3 ways as a sum of consecutive naturals, for example, 243740 + ... + 243821.

It is an arithmetic number, because the mean of its divisors is an integer number (5119401).

Almost surely, 2^19990001 is an apocalyptic number.

19990001 is the 2000-th centered decagonal number.

It is an amenable number.

19990001 is a deficient number, since it is larger than the sum of its proper divisors (487603).

19990001 is an equidigital number, since it uses as much as digits as its factorization.

19990001 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 487602.

The product of its (nonzero) digits is 729, while the sum is 29.

The square root of 19990001 is about 4471.0178930530. The cubic root of 19990001 is about 271.3965183493.

Adding to 19990001 its reverse (10009991), we get a palindrome (29999992).

The spelling of 19990001 in words is "nineteen million, nine hundred ninety thousand, one".