18871639 has 2 divisors, whose sum is σ = 18871640. Its totient is φ = 18871638.

The previous prime is 18871609. The next prime is 18871667. The reversal of 18871639 is 93617881.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 18871639 - 2⁵ = 18871607 is a prime.

It is a super-2 number, since 2×18871639² = 712277517092642, which contains 22 as substring.

It is a junction number, because it is equal to n+sod(n) for n = 18871595 and 18871604.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (18871609) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9435819 + 9435820.

It is an arithmetic number, because the mean of its divisors is an integer number (9435820).

Almost surely, 2^18871639 is an apocalyptic number.

18871639 is a deficient number, since it is larger than the sum of its proper divisors (1).

18871639 is an equidigital number, since it uses as much as digits as its factorization.

18871639 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 72576, while the sum is 43.

The square root of 18871639 is about 4344.1499743908. The cubic root of 18871639 is about 266.2378965455.

The spelling of 18871639 in words is "eighteen million, eight hundred seventy-one thousand, six hundred thirty-nine".