21709491061 has 2 divisors, whose sum is σ = 21709491062. Its totient is φ = 21709491060.

The previous prime is 21709491049. The next prime is 21709491077. The reversal of 21709491061 is 16019490712.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 21636644836 + 72846225 = 147094^2 + 8535^2 .

It is a cyclic number.

It is not a de Polignac number, because 21709491061 - 2²¹ = 21707393909 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21709491761) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10854745530 + 10854745531.

It is an arithmetic number, because the mean of its divisors is an integer number (10854745531).

Almost surely, 2^21709491061 is an apocalyptic number.

It is an amenable number.

21709491061 is a deficient number, since it is larger than the sum of its proper divisors (1).

21709491061 is an equidigital number, since it uses as much as digits as its factorization.

21709491061 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 27216, while the sum is 40.

The spelling of 21709491061 in words is "twenty-one billion, seven hundred nine million, four hundred ninety-one thousand, sixty-one".