18691291 has 2 divisors, whose sum is σ = 18691292. Its totient is φ = 18691290.

The previous prime is 18691273. The next prime is 18691297. The reversal of 18691291 is 19219681.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 18691291 - 2¹¹ = 18689243 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 18691291.

It is not a weakly prime, because it can be changed into another prime (18691297) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9345645 + 9345646.

It is an arithmetic number, because the mean of its divisors is an integer number (9345646).

Almost surely, 2^18691291 is an apocalyptic number.

18691291 is a deficient number, since it is larger than the sum of its proper divisors (1).

18691291 is an equidigital number, since it uses as much as digits as its factorization.

18691291 is an evil number, because the sum of its binary digits is even.

The product of its digits is 7776, while the sum is 37.

The square root of 18691291 is about 4323.3425725936. The cubic root of 18691291 is about 265.3870740718.

It can be divided in two parts, 1869 and 1291, that added together give a triangular number (3160 = T₇₉).

The spelling of 18691291 in words is "eighteen million, six hundred ninety-one thousand, two hundred ninety-one".