21210020201609 has 2 divisors, whose sum is σ = 21210020201610. Its totient is φ = 21210020201608.

The previous prime is 21210020201603. The next prime is 21210020201647. The reversal of 21210020201609 is 90610202001212.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 16124079630400 + 5085940571209 = 4015480^2 + 2255203^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21210020201609 is a prime.

It is not a weakly prime, because it can be changed into another prime (21210020201603) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10605010100804 + 10605010100805.

It is an arithmetic number, because the mean of its divisors is an integer number (10605010100805).

Almost surely, 2^{21210020201609} is an apocalyptic number.

It is an amenable number.

21210020201609 is a deficient number, since it is larger than the sum of its proper divisors (1).

21210020201609 is an equidigital number, since it uses as much as digits as its factorization.

21210020201609 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 864, while the sum is 26.

The spelling of 21210020201609 in words is "twenty-one trillion, two hundred ten billion, twenty million, two hundred one thousand, six hundred nine".