209521213441 has 4 divisors (see below), whose sum is σ = 216746082900. Its totient is φ = 202296343984.

The previous prime is 209521213417. The next prime is 209521213477. The reversal of 209521213441 is 144312125902.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 119563808400 + 89957405041 = 345780^2 + 299929^2 .

It is a cyclic number.

It is not a de Polignac number, because 209521213441 - 2⁷ = 209521213313 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 209521213397 and 209521213406.

It is not an unprimeable number, because it can be changed into a prime (209521213411) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 3612434686 + ... + 3612434743.

It is an arithmetic number, because the mean of its divisors is an integer number (54186520725).

It is a Proth number, since it is equal to 199815 ⋅ 2²⁰ + 1 and 199815 < 2²⁰.

Almost surely, 2^209521213441 is an apocalyptic number.

It is an amenable number.

209521213441 is a deficient number, since it is larger than the sum of its proper divisors (7224869459).

209521213441 is an equidigital number, since it uses as much as digits as its factorization.

209521213441 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7224869458.

The product of its (nonzero) digits is 17280, while the sum is 34.

The spelling of 209521213441 in words is "two hundred nine billion, five hundred twenty-one million, two hundred thirteen thousand, four hundred forty-one".