21406556329 has 2 divisors, whose sum is σ = 21406556330. Its totient is φ = 21406556328.

The previous prime is 21406556309. The next prime is 21406556377. The reversal of 21406556329 is 92365560412.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 18320976025 + 3085580304 = 135355^2 + 55548^2 .

It is a cyclic number.

It is not a de Polignac number, because 21406556329 - 2¹⁵ = 21406523561 is a prime.

It is not a weakly prime, because it can be changed into another prime (21406556309) 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, 10703278164 + 10703278165.

It is an arithmetic number, because the mean of its divisors is an integer number (10703278165).

Almost surely, 2^21406556329 is an apocalyptic number.

It is an amenable number.

21406556329 is a deficient number, since it is larger than the sum of its proper divisors (1).

21406556329 is an equidigital number, since it uses as much as digits as its factorization.

21406556329 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 388800, while the sum is 43.

The spelling of 21406556329 in words is "twenty-one billion, four hundred six million, five hundred fifty-six thousand, three hundred twenty-nine".