18871631 has 4 divisors (see below), whose sum is σ = 19181064. Its totient is φ = 18562200.

The previous prime is 18871609. The next prime is 18871639. The reversal of 18871631 is 13617881.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 18871631 - 2¹⁴ = 18855247 is a prime.

It is a super-2 number, since 2×18871631² = 712276913200322, which contains 22 as substring.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 18871591 and 18871600.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (18871639) 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 in 3 ways as a sum of consecutive naturals, for example, 154625 + ... + 154746.

It is an arithmetic number, because the mean of its divisors is an integer number (4795266).

Almost surely, 2^18871631 is an apocalyptic number.

18871631 is a deficient number, since it is larger than the sum of its proper divisors (309433).

18871631 is an equidigital number, since it uses as much as digits as its factorization.

18871631 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 309432.

The product of its digits is 8064, while the sum is 35.

The square root of 18871631 is about 4344.1490536122. The cubic root of 18871631 is about 266.2378589246.

The spelling of 18871631 in words is "eighteen million, eight hundred seventy-one thousand, six hundred thirty-one".