21206672689 has 2 divisors, whose sum is σ = 21206672690. Its totient is φ = 21206672688.

The previous prime is 21206672671. The next prime is 21206672713. The reversal of 21206672689 is 98627660212.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 21167922064 + 38750625 = 145492^2 + 6225^2 .

It is a cyclic number.

It is not a de Polignac number, because 21206672689 - 2²⁹ = 20669801777 is a prime.

It is not a weakly prime, because it can be changed into another prime (21206672629) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10603336344 + 10603336345.

It is an arithmetic number, because the mean of its divisors is an integer number (10603336345).

Almost surely, 2^21206672689 is an apocalyptic number.

It is an amenable number.

21206672689 is a deficient number, since it is larger than the sum of its proper divisors (1).

21206672689 is an equidigital number, since it uses as much as digits as its factorization.

21206672689 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 870912, while the sum is 49.

The spelling of 21206672689 in words is "twenty-one billion, two hundred six million, six hundred seventy-two thousand, six hundred eighty-nine".