19863801721 has 3 divisors (see below), whose sum is σ = 19863942661. Its totient is φ = 19863660782.

The previous prime is 19863801689. The next prime is 19863801733. The reversal of 19863801721 is 12710836891.

It is a happy number.

The square root of 19863801721 is 140939.

It is a perfect power (a square), and thus also a powerful number.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length.

It is not a de Polignac number, because 19863801721 - 2⁵ = 19863801689 is a prime.

It is a super-2 number, since 2×19863801721² (a number of 21 digits) contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (19863801781) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (23) of ones.

It is a polite number, since it can be written in 2 ways as a sum of consecutive naturals, for example, 70470 + ... + 211408.

Almost surely, 2^19863801721 is an apocalyptic number.

19863801721 is the 140939-th square number.

19863801721 is the 70470-th centered octagonal number.

It is an amenable number.

19863801721 is a deficient number, since it is larger than the sum of its proper divisors (140940).

19863801721 is an frugal number, since it uses more digits than its factorization.

19863801721 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 281878 (or 140939 counting only the distinct ones).

The product of its (nonzero) digits is 145152, while the sum is 46.

The spelling of 19863801721 in words is "nineteen billion, eight hundred sixty-three million, eight hundred one thousand, seven hundred twenty-one".