18671521 has 4 divisors (see below), whose sum is σ = 20368944. Its totient is φ = 16974100.

The previous prime is 18671519. The next prime is 18671537. The reversal of 18671521 is 12517681.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is not a de Polignac number, because 18671521 - 2¹ = 18671519 is a prime.

It is a Smith number, since the sum of its digits (31) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (18671501) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 848695 + ... + 848716.

It is an arithmetic number, because the mean of its divisors is an integer number (5092236).

Almost surely, 2^18671521 is an apocalyptic number.

18671521 is a gapful number since it is divisible by the number (11) formed by its first and last digit.

It is an amenable number.

18671521 is a deficient number, since it is larger than the sum of its proper divisors (1697423).

18671521 is a wasteful number, since it uses less digits than its factorization.

18671521 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1697422.

The product of its digits is 3360, while the sum is 31.

The square root of 18671521 is about 4321.0555423415. The cubic root of 18671521 is about 265.2934733787.

The spelling of 18671521 in words is "eighteen million, six hundred seventy-one thousand, five hundred twenty-one".