18135521 has 2 divisors, whose sum is σ = 18135522. Its totient is φ = 18135520.

The previous prime is 18135517. The next prime is 18135539. The reversal of 18135521 is 12553181.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 17305600 + 829921 = 4160^2 + 911^2 .

It is a cyclic number.

It is not a de Polignac number, because 18135521 - 2² = 18135517 is a prime.

It is a Sophie Germain prime.

It is a Curzon number.

It is not a weakly prime, because it can be changed into another prime (18135581) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9067760 + 9067761.

It is an arithmetic number, because the mean of its divisors is an integer number (9067761).

Almost surely, 2^18135521 is an apocalyptic number.

It is an amenable number.

18135521 is a deficient number, since it is larger than the sum of its proper divisors (1).

18135521 is an equidigital number, since it uses as much as digits as its factorization.

18135521 is an evil number, because the sum of its binary digits is even.

The product of its digits is 1200, while the sum is 26.

The square root of 18135521 is about 4258.5820410085. The cubic root of 18135521 is about 262.7302095389.

The spelling of 18135521 in words is "eighteen million, one hundred thirty-five thousand, five hundred twenty-one".