21206555297 has 2 divisors, whose sum is σ = 21206555298. Its totient is φ = 21206555296.

The previous prime is 21206555273. The next prime is 21206555339. The reversal of 21206555297 is 79255560212.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 20310810256 + 895745041 = 142516^2 + 29929^2 .

It is a cyclic number.

It is not a de Polignac number, because 21206555297 - 2⁶ = 21206555233 is a prime.

It is not a weakly prime, because it can be changed into another prime (21206555207) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10603277648 + 10603277649.

It is an arithmetic number, because the mean of its divisors is an integer number (10603277649).

Almost surely, 2^21206555297 is an apocalyptic number.

It is an amenable number.

21206555297 is a deficient number, since it is larger than the sum of its proper divisors (1).

21206555297 is an equidigital number, since it uses as much as digits as its factorization.

21206555297 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 378000, while the sum is 44.

The spelling of 21206555297 in words is "twenty-one billion, two hundred six million, five hundred fifty-five thousand, two hundred ninety-seven".