19271981 has 2 divisors, whose sum is σ = 19271982. Its totient is φ = 19271980.

The previous prime is 19271969. The next prime is 19271983. The reversal of 19271981 is 18917291.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 16240900 + 3031081 = 4030^2 + 1741^2 .

It is a cyclic number.

It is not a de Polignac number, because 19271981 - 2¹⁴ = 19255597 is a prime.

It is a super-2 number, since 2×19271981² = 742818503328722, which contains 22 as substring.

It is a Sophie Germain prime.

Together with 19271983, it forms a pair of twin primes.

It is a Chen prime.

It is a Curzon number.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (19271983) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9635990 + 9635991.

It is an arithmetic number, because the mean of its divisors is an integer number (9635991).

Almost surely, 2^19271981 is an apocalyptic number.

It is an amenable number.

19271981 is a deficient number, since it is larger than the sum of its proper divisors (1).

19271981 is an equidigital number, since it uses as much as digits as its factorization.

19271981 is an evil number, because the sum of its binary digits is even.

The product of its digits is 9072, while the sum is 38.

The square root of 19271981 is about 4389.9864464483. The cubic root of 19271981 is about 268.1073908739.

The spelling of 19271981 in words is "nineteen million, two hundred seventy-one thousand, nine hundred eighty-one".