221857397 has 2 divisors, whose sum is σ = 221857398. Its totient is φ = 221857396.

The previous prime is 221857381. The next prime is 221857399. The reversal of 221857397 is 793758122.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 159542161 + 62315236 = 12631^2 + 7894^2 .

It is a cyclic number.

It is not a de Polignac number, because 221857397 - 2⁴ = 221857381 is a prime.

Together with 221857399, it forms a pair of twin primes.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (221857399) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 110928698 + 110928699.

It is an arithmetic number, because the mean of its divisors is an integer number (110928699).

Almost surely, 2^221857397 is an apocalyptic number.

It is an amenable number.

221857397 is a deficient number, since it is larger than the sum of its proper divisors (1).

221857397 is an equidigital number, since it uses as much as digits as its factorization.

221857397 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 211680, while the sum is 44.

The square root of 221857397 is about 14894.8782136679. The cubic root of 221857397 is about 605.3752170091.

The spelling of 221857397 in words is "two hundred twenty-one million, eight hundred fifty-seven thousand, three hundred ninety-seven".