21010066261 has 2 divisors, whose sum is σ = 21010066262. Its totient is φ = 21010066260.

The previous prime is 21010066229. The next prime is 21010066283. The reversal of 21010066261 is 16266001012.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 20476179025 + 533887236 = 143095^2 + 23106^2 .

It is a cyclic number.

It is not a de Polignac number, because 21010066261 - 2⁵ = 21010066229 is a prime.

It is a super-2 number, since 2×21010066261² (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 (21010066291) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10505033130 + 10505033131.

It is an arithmetic number, because the mean of its divisors is an integer number (10505033131).

Almost surely, 2^21010066261 is an apocalyptic number.

It is an amenable number.

21010066261 is a deficient number, since it is larger than the sum of its proper divisors (1).

21010066261 is an equidigital number, since it uses as much as digits as its factorization.

21010066261 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 864, while the sum is 25.

Adding to 21010066261 its reverse (16266001012), we get a palindrome (37276067273).

The spelling of 21010066261 in words is "twenty-one billion, ten million, sixty-six thousand, two hundred sixty-one".