18687491 has 2 divisors, whose sum is σ = 18687492. Its totient is φ = 18687490.

The previous prime is 18687481. The next prime is 18687497. The reversal of 18687491 is 19478681.

It is a strong prime.

It is an emirp because it is prime and its reverse (19478681) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 18687491 - 2¹⁸ = 18425347 is a prime.

It is not a weakly prime, because it can be changed into another prime (18687497) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9343745 + 9343746.

It is an arithmetic number, because the mean of its divisors is an integer number (9343746).

Almost surely, 2^18687491 is an apocalyptic number.

18687491 is a deficient number, since it is larger than the sum of its proper divisors (1).

18687491 is an equidigital number, since it uses as much as digits as its factorization.

18687491 is an evil number, because the sum of its binary digits is even.

The product of its digits is 96768, while the sum is 44.

The square root of 18687491 is about 4322.9030754806. The cubic root of 18687491 is about 265.3690881689.

The spelling of 18687491 in words is "eighteen million, six hundred eighty-seven thousand, four hundred ninety-one".