21243937009 has 3 divisors (see below), whose sum is σ = 21244082763. Its totient is φ = 21243791256.

The previous prime is 21243937003. The next prime is 21243937019. The reversal of 21243937009 is 90073934212.

The square root of 21243937009 is 145753.

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., 9303567025 + 11940369984 = 96455^2 + 109272^2 .

It is not a de Polignac number, because 21243937009 - 2⁵ = 21243936977 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21243937003) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 2 ways as a sum of consecutive naturals, for example, 72877 + ... + 218629.

It is an arithmetic number, because the mean of its divisors is an integer number (7081360921).

Almost surely, 2^21243937009 is an apocalyptic number.

21243937009 is the 145753-rd square number.

21243937009 is the 72877-th centered octagonal number.

It is an amenable number.

21243937009 is a deficient number, since it is larger than the sum of its proper divisors (145754).

21243937009 is an frugal number, since it uses more digits than its factorization.

21243937009 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 291506 (or 145753 counting only the distinct ones).

The product of its (nonzero) digits is 81648, while the sum is 40.

The spelling of 21243937009 in words is "twenty-one billion, two hundred forty-three million, nine hundred thirty-seven thousand, nine".