18613891 has 2 divisors, whose sum is σ = 18613892. Its totient is φ = 18613890.

The previous prime is 18613871. The next prime is 18613897. The reversal of 18613891 is 19831681.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 18613891 - 2¹¹ = 18611843 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 18613891.

It is not a weakly prime, because it can be changed into another prime (18613897) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9306945 + 9306946.

It is an arithmetic number, because the mean of its divisors is an integer number (9306946).

Almost surely, 2^18613891 is an apocalyptic number.

18613891 is a deficient number, since it is larger than the sum of its proper divisors (1).

18613891 is an equidigital number, since it uses as much as digits as its factorization.

18613891 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 10368, while the sum is 37.

The square root of 18613891 is about 4314.3818792499. The cubic root of 18613891 is about 265.0202476519.

The spelling of 18613891 in words is "eighteen million, six hundred thirteen thousand, eight hundred ninety-one".