21571266209 has 2 divisors, whose sum is σ = 21571266210. Its totient is φ = 21571266208.

The previous prime is 21571266173. The next prime is 21571266263. The reversal of 21571266209 is 90266217512.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 19584603025 + 1986663184 = 139945^2 + 44572^2 .

It is a cyclic number.

It is not a de Polignac number, because 21571266209 - 2²⁴ = 21554488993 is a prime.

It is not a weakly prime, because it can be changed into another prime (21571260209) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10785633104 + 10785633105.

It is an arithmetic number, because the mean of its divisors is an integer number (10785633105).

Almost surely, 2^21571266209 is an apocalyptic number.

It is an amenable number.

21571266209 is a deficient number, since it is larger than the sum of its proper divisors (1).

21571266209 is an equidigital number, since it uses as much as digits as its factorization.

21571266209 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 90720, while the sum is 41.

The spelling of 21571266209 in words is "twenty-one billion, five hundred seventy-one million, two hundred sixty-six thousand, two hundred nine".