19681909 has 6 divisors (see below), whose sum is σ = 21312546. Its totient is φ = 18167760.

The previous prime is 19681897. The next prime is 19681913. The reversal of 19681909 is 90918691.

It can be written as a sum of positive squares in 3 ways, for example, as 1380625 + 18301284 = 1175^2 + 4278^2 .

It is not a de Polignac number, because 19681909 - 2¹¹ = 19679861 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (19681919) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 58062 + ... + 58399.

It is an arithmetic number, because the mean of its divisors is an integer number (3552091).

Almost surely, 2^19681909 is an apocalyptic number.

It is an amenable number.

19681909 is a deficient number, since it is larger than the sum of its proper divisors (1630637).

19681909 is a wasteful number, since it uses less digits than its factorization.

19681909 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 116487 (or 116474 counting only the distinct ones).

The product of its (nonzero) digits is 34992, while the sum is 43.

The square root of 19681909 is about 4436.4297582628. The cubic root of 19681909 is about 269.9950113390.

The spelling of 19681909 in words is "nineteen million, six hundred eighty-one thousand, nine hundred nine".