21783206909 has 2 divisors, whose sum is σ = 21783206910. Its totient is φ = 21783206908.

The previous prime is 21783206903. The next prime is 21783206927. The reversal of 21783206909 is 90960238712.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 20357011684 + 1426195225 = 142678^2 + 37765^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21783206909 is a prime.

It is a super-3 number, since 3×21783206909³ (a number of 32 digits) contains 333 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21783206903) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10891603454 + 10891603455.

It is an arithmetic number, because the mean of its divisors is an integer number (10891603455).

Almost surely, 2^21783206909 is an apocalyptic number.

It is an amenable number.

21783206909 is a deficient number, since it is larger than the sum of its proper divisors (1).

21783206909 is an equidigital number, since it uses as much as digits as its factorization.

21783206909 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 326592, while the sum is 47.

The spelling of 21783206909 in words is "twenty-one billion, seven hundred eighty-three million, two hundred six thousand, nine hundred nine".