1919115721 has 2 divisors, whose sum is σ = 1919115722. Its totient is φ = 1919115720.

The previous prime is 1919115707. The next prime is 1919115733. The reversal of 1919115721 is 1275119191.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 1305810496 + 613305225 = 36136^2 + 24765^2 .

It is a cyclic number.

It is not a de Polignac number, because 1919115721 - 2⁵ = 1919115689 is a prime.

It is not a weakly prime, because it can be changed into another prime (1919115521) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 959557860 + 959557861.

It is an arithmetic number, because the mean of its divisors is an integer number (959557861).

Almost surely, 2^1919115721 is an apocalyptic number.

It is an amenable number.

1919115721 is a deficient number, since it is larger than the sum of its proper divisors (1).

1919115721 is an equidigital number, since it uses as much as digits as its factorization.

1919115721 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 5670, while the sum is 37.

The square root of 1919115721 is about 43807.7130309264. The cubic root of 1919115721 is about 1242.7021633271.

The spelling of 1919115721 in words is "one billion, nine hundred nineteen million, one hundred fifteen thousand, seven hundred twenty-one".