19228721 has 2 divisors, whose sum is σ = 19228722. Its totient is φ = 19228720.

The previous prime is 19228673. The next prime is 19228723. The reversal of 19228721 is 12782291.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 9834496 + 9394225 = 3136^2 + 3065^2 .

It is a cyclic number.

It is not a de Polignac number, because 19228721 - 2²² = 15034417 is a prime.

It is a super-2 number, since 2×19228721² = 739487422591682, which contains 22 as substring.

It is a Sophie Germain prime.

Together with 19228723, it forms a pair of twin primes.

It is a Chen prime.

It is a Curzon number.

It is not a weakly prime, because it can be changed into another prime (19228723) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9614360 + 9614361.

It is an arithmetic number, because the mean of its divisors is an integer number (9614361).

Almost surely, 2^19228721 is an apocalyptic number.

It is an amenable number.

19228721 is a deficient number, since it is larger than the sum of its proper divisors (1).

19228721 is an equidigital number, since it uses as much as digits as its factorization.

19228721 is an evil number, because the sum of its binary digits is even.

The product of its digits is 4032, while the sum is 32.

The square root of 19228721 is about 4385.0565560777. The cubic root of 19228721 is about 267.9066328433.

The spelling of 19228721 in words is "nineteen million, two hundred twenty-eight thousand, seven hundred twenty-one".