21203750191009 has 3 divisors (see below), whose sum is σ = 21203754795763. Its totient is φ = 21203745586256.

The previous prime is 21203750191007. The next prime is 21203750191027. The reversal of 21203750191009 is 90019105730212.

The square root of 21203750191009 is 4604753.

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 can be written as a sum of positive squares in only one way, i.e., 4169376029025 + 17034374161984 = 2041905^2 + 4127272^2 .

It is not a de Polignac number, because 21203750191009 - 2¹ = 21203750191007 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21203750191007) by changing a digit.

It is a polite number, since it can be written in 2 ways as a sum of consecutive naturals, for example, 2302377 + ... + 6907129.

Almost surely, 2^{21203750191009} is an apocalyptic number.

21203750191009 is the 4604753-rd square number.

21203750191009 is the 2302377-th centered octagonal number.

It is an amenable number.

21203750191009 is a deficient number, since it is larger than the sum of its proper divisors (4604754).

21203750191009 is an frugal number, since it uses more digits than its factorization.

21203750191009 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 9209506 (or 4604753 counting only the distinct ones).

The product of its (nonzero) digits is 34020, while the sum is 40.

The spelling of 21203750191009 in words is "twenty-one trillion, two hundred three billion, seven hundred fifty million, one hundred ninety-one thousand, nine".