19904981 has 2 divisors, whose sum is σ = 19904982. Its totient is φ = 19904980.

The previous prime is 19904953. The next prime is 19904987. The reversal of 19904981 is 18940991.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 19280881 + 624100 = 4391^2 + 790^2 .

It is an emirp because it is prime and its reverse (18940991) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 19904981 - 2⁶ = 19904917 is a prime.

It is a super-2 number, since 2×19904981² = 792416537220722, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (19904987) by changing a digit.

It is a good prime.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9952490 + 9952491.

It is an arithmetic number, because the mean of its divisors is an integer number (9952491).

Almost surely, 2^19904981 is an apocalyptic number.

It is an amenable number.

19904981 is a deficient number, since it is larger than the sum of its proper divisors (1).

19904981 is an equidigital number, since it uses as much as digits as its factorization.

19904981 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 23328, while the sum is 41.

The square root of 19904981 is about 4461.4998599126. The cubic root of 19904981 is about 271.0112103495.

The spelling of 19904981 in words is "nineteen million, nine hundred four thousand, nine hundred eighty-one".