19776221 has 2 divisors, whose sum is σ = 19776222. Its totient is φ = 19776220.

The previous prime is 19776209. The next prime is 19776223. The reversal of 19776221 is 12267791.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 19624900 + 151321 = 4430^2 + 389^2 .

It is an emirp because it is prime and its reverse (12267791) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 19776221 - 2⁶ = 19776157 is a prime.

Together with 19776223, 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 (19776223) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9888110 + 9888111.

It is an arithmetic number, because the mean of its divisors is an integer number (9888111).

Almost surely, 2^19776221 is an apocalyptic number.

It is an amenable number.

19776221 is a deficient number, since it is larger than the sum of its proper divisors (1).

19776221 is an equidigital number, since it uses as much as digits as its factorization.

19776221 is an evil number, because the sum of its binary digits is even.

The product of its digits is 10584, while the sum is 35.

The square root of 19776221 is about 4447.0463231228. The cubic root of 19776221 is about 270.4255794123.

The spelling of 19776221 in words is "nineteen million, seven hundred seventy-six thousand, two hundred twenty-one".