1921678709 has 2 divisors, whose sum is σ = 1921678710. Its totient is φ = 1921678708.

The previous prime is 1921678679. The next prime is 1921678711. The reversal of 1921678709 is 9078761291.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 1920367684 + 1311025 = 43822^2 + 1145^2 .

It is a cyclic number.

It is not a de Polignac number, because 1921678709 - 2¹² = 1921674613 is a prime.

Together with 1921678711, 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 (1921678769) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 960839354 + 960839355.

It is an arithmetic number, because the mean of its divisors is an integer number (960839355).

Almost surely, 2^1921678709 is an apocalyptic number.

It is an amenable number.

1921678709 is a deficient number, since it is larger than the sum of its proper divisors (1).

1921678709 is an equidigital number, since it uses as much as digits as its factorization.

1921678709 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 381024, while the sum is 50.

The square root of 1921678709 is about 43836.9559732425. The cubic root of 1921678709 is about 1243.2551287500.

The spelling of 1921678709 in words is "one billion, nine hundred twenty-one million, six hundred seventy-eight thousand, seven hundred nine".