18718521 has 16 divisors (see below), whose sum is σ = 25534080. Its totient is φ = 12193920.

The previous prime is 18718519. The next prime is 18718523. The reversal of 18718521 is 12581781.

It is an interprime number because it is at equal distance from previous prime (18718519) and next prime (18718523).

It is not a de Polignac number, because 18718521 - 2¹ = 18718519 is a prime.

It is not an unprimeable number, because it can be changed into a prime (18718523) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 42420 + ... + 42858.

It is an arithmetic number, because the mean of its divisors is an integer number (1595880).

Almost surely, 2^18718521 is an apocalyptic number.

It is an amenable number.

18718521 is a deficient number, since it is larger than the sum of its proper divisors (6815559).

18718521 is a wasteful number, since it uses less digits than its factorization.

18718521 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 736.

The product of its digits is 4480, while the sum is 33.

The square root of 18718521 is about 4326.4906101828. The cubic root of 18718521 is about 265.5158859984.

The spelling of 18718521 in words is "eighteen million, seven hundred eighteen thousand, five hundred twenty-one".