21709491049 has 2 divisors, whose sum is σ = 21709491050. Its totient is φ = 21709491048.

The previous prime is 21709491043. The next prime is 21709491061. The reversal of 21709491049 is 94019490712.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 21697290000 + 12201049 = 147300^2 + 3493^2 .

It is a cyclic number.

It is not a de Polignac number, because 21709491049 - 2⁵ = 21709491017 is a prime.

It is a super-2 number, since 2×21709491049² (a number of 21 digits) contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (21709491043) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10854745524 + 10854745525.

It is an arithmetic number, because the mean of its divisors is an integer number (10854745525).

Almost surely, 2^21709491049 is an apocalyptic number.

It is an amenable number.

21709491049 is a deficient number, since it is larger than the sum of its proper divisors (1).

21709491049 is an equidigital number, since it uses as much as digits as its factorization.

21709491049 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 163296, while the sum is 46.

The spelling of 21709491049 in words is "twenty-one billion, seven hundred nine million, four hundred ninety-one thousand, forty-nine".