19685921 has 2 divisors, whose sum is σ = 19685922. Its totient is φ = 19685920.

The previous prime is 19685917. The next prime is 19685929. The reversal of 19685921 is 12958691.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 15840400 + 3845521 = 3980^2 + 1961^2 .

It is an emirp because it is prime and its reverse (12958691) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 19685921 - 2² = 19685917 is a prime.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (19685929) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9842960 + 9842961.

It is an arithmetic number, because the mean of its divisors is an integer number (9842961).

Almost surely, 2^19685921 is an apocalyptic number.

It is an amenable number.

19685921 is a deficient number, since it is larger than the sum of its proper divisors (1).

19685921 is an equidigital number, since it uses as much as digits as its factorization.

19685921 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 38880, while the sum is 41.

The square root of 19685921 is about 4436.8819006144. The cubic root of 19685921 is about 270.0133555351.

The spelling of 19685921 in words is "nineteen million, six hundred eighty-five thousand, nine hundred twenty-one".