21682493909 has 2 divisors, whose sum is σ = 21682493910. Its totient is φ = 21682493908.

The previous prime is 21682493893. The next prime is 21682493933. The reversal of 21682493909 is 90939428612.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 21167340100 + 515153809 = 145490^2 + 22697^2 .

It is a cyclic number.

It is not a de Polignac number, because 21682493909 - 2⁴ = 21682493893 is a prime.

It is a super-2 number, since 2×21682493909² (a number of 21 digits) contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21682493939) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10841246954 + 10841246955.

It is an arithmetic number, because the mean of its divisors is an integer number (10841246955).

Almost surely, 2^21682493909 is an apocalyptic number.

It is an amenable number.

21682493909 is a deficient number, since it is larger than the sum of its proper divisors (1).

21682493909 is an equidigital number, since it uses as much as digits as its factorization.

21682493909 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 1679616, while the sum is 53.

The spelling of 21682493909 in words is "twenty-one billion, six hundred eighty-two million, four hundred ninety-three thousand, nine hundred nine".