221551409 has 2 divisors, whose sum is σ = 221551410. Its totient is φ = 221551408.

The previous prime is 221551357. The next prime is 221551411. The reversal of 221551409 is 904155122.

221551409 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 162307600 + 59243809 = 12740^2 + 7697^2 .

It is a cyclic number.

It is not a de Polignac number, because 221551409 - 2²⁰ = 220502833 is a prime.

Together with 221551411, it forms a pair of twin primes.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (221551439) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 110775704 + 110775705.

It is an arithmetic number, because the mean of its divisors is an integer number (110775705).

Almost surely, 2^221551409 is an apocalyptic number.

It is an amenable number.

221551409 is a deficient number, since it is larger than the sum of its proper divisors (1).

221551409 is an equidigital number, since it uses as much as digits as its factorization.

221551409 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 3600, while the sum is 29.

The square root of 221551409 is about 14884.6030850675. The cubic root of 221551409 is about 605.0967757217.

The spelling of 221551409 in words is "two hundred twenty-one million, five hundred fifty-one thousand, four hundred nine".