18991949 has 2 divisors, whose sum is σ = 18991950. Its totient is φ = 18991948.

The previous prime is 18991937. The next prime is 18991969. The reversal of 18991949 is 94919981.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 18748900 + 243049 = 4330^2 + 493^2 .

It is a cyclic number.

It is not a de Polignac number, because 18991949 - 2¹² = 18987853 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 18991897 and 18991906.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (18991909) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9495974 + 9495975.

It is an arithmetic number, because the mean of its divisors is an integer number (9495975).

Almost surely, 2^18991949 is an apocalyptic number.

It is an amenable number.

18991949 is a deficient number, since it is larger than the sum of its proper divisors (1).

18991949 is an equidigital number, since it uses as much as digits as its factorization.

18991949 is an evil number, because the sum of its binary digits is even.

The product of its digits is 209952, while the sum is 50.

The square root of 18991949 is about 4357.9753326516. The cubic root of 18991949 is about 266.8024695445.

The spelling of 18991949 in words is "eighteen million, nine hundred ninety-one thousand, nine hundred forty-nine".