18948991 has 2 divisors, whose sum is σ = 18948992. Its totient is φ = 18948990.

The previous prime is 18948973. The next prime is 18948997. The reversal of 18948991 is 19984981.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 18948991 - 2⁵ = 18948959 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (18948997) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9474495 + 9474496.

It is an arithmetic number, because the mean of its divisors is an integer number (9474496).

Almost surely, 2^18948991 is an apocalyptic number.

18948991 is a deficient number, since it is larger than the sum of its proper divisors (1).

18948991 is an equidigital number, since it uses as much as digits as its factorization.

18948991 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 186624, while the sum is 49.

The square root of 18948991 is about 4353.0438775643. The cubic root of 18948991 is about 266.6011569984.

The spelling of 18948991 in words is "eighteen million, nine hundred forty-eight thousand, nine hundred ninety-one".