21345130661 has 2 divisors, whose sum is σ = 21345130662. Its totient is φ = 21345130660.

The previous prime is 21345130571. The next prime is 21345130679. The reversal of 21345130661 is 16603154312.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 15355918561 + 5989212100 = 123919^2 + 77390^2 .

It is a cyclic number.

It is not a de Polignac number, because 21345130661 - 2¹⁴ = 21345114277 is a prime.

It is a super-2 number, since 2×21345130661² (a number of 21 digits) contains 22 as substring.

It is a Sophie Germain prime.

It is a Curzon number.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21345132661) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10672565330 + 10672565331.

It is an arithmetic number, because the mean of its divisors is an integer number (10672565331).

Almost surely, 2^21345130661 is an apocalyptic number.

It is an amenable number.

21345130661 is a deficient number, since it is larger than the sum of its proper divisors (1).

21345130661 is an equidigital number, since it uses as much as digits as its factorization.

21345130661 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 12960, while the sum is 32.

Adding to 21345130661 its reverse (16603154312), we get a palindrome (37948284973).

The spelling of 21345130661 in words is "twenty-one billion, three hundred forty-five million, one hundred thirty thousand, six hundred sixty-one".