21043653109 has 2 divisors, whose sum is σ = 21043653110. Its totient is φ = 21043653108.

The previous prime is 21043653077. The next prime is 21043653131. The reversal of 21043653109 is 90135634012.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 13063804209 + 7979848900 = 114297^2 + 89330^2 .

It is a cyclic number.

It is not a de Polignac number, because 21043653109 - 2⁵ = 21043653077 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21043653139) 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, 10521826554 + 10521826555.

It is an arithmetic number, because the mean of its divisors is an integer number (10521826555).

Almost surely, 2^21043653109 is an apocalyptic number.

It is an amenable number.

21043653109 is a deficient number, since it is larger than the sum of its proper divisors (1).

21043653109 is an equidigital number, since it uses as much as digits as its factorization.

21043653109 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 19440, while the sum is 34.

The spelling of 21043653109 in words is "twenty-one billion, forty-three million, six hundred fifty-three thousand, one hundred nine".