221894509 has 2 divisors, whose sum is σ = 221894510. Its totient is φ = 221894508.

The previous prime is 221894507. The next prime is 221894539. The reversal of 221894509 is 905498122.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 144841225 + 77053284 = 12035^2 + 8778^2 .

It is a cyclic number.

It is not a de Polignac number, because 221894509 - 2¹ = 221894507 is a prime.

Together with 221894507, it forms a pair of twin primes.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (221894507) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 110947254 + 110947255.

It is an arithmetic number, because the mean of its divisors is an integer number (110947255).

Almost surely, 2^221894509 is an apocalyptic number.

It is an amenable number.

221894509 is a deficient number, since it is larger than the sum of its proper divisors (1).

221894509 is an equidigital number, since it uses as much as digits as its factorization.

221894509 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 51840, while the sum is 40.

The square root of 221894509 is about 14896.1239589364. The cubic root of 221894509 is about 605.4089705715.

The spelling of 221894509 in words is "two hundred twenty-one million, eight hundred ninety-four thousand, five hundred nine".