18306521 has 4 divisors (see below), whose sum is σ = 18407844. Its totient is φ = 18205200.

The previous prime is 18306517. The next prime is 18306539. The reversal of 18306521 is 12560381.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 12560381 = 677 ⋅18553.

It can be written as a sum of positive squares in 2 ways, for example, as 6056521 + 12250000 = 2461^2 + 3500^2 .

It is a cyclic number.

It is not a de Polignac number, because 18306521 - 2² = 18306517 is a prime.

It is a super-2 number, since 2×18306521² = 670257422246882, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (18306581) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 50390 + ... + 50751.

It is an arithmetic number, because the mean of its divisors is an integer number (4601961).

Almost surely, 2^18306521 is an apocalyptic number.

It is an amenable number.

18306521 is a deficient number, since it is larger than the sum of its proper divisors (101323).

18306521 is a wasteful number, since it uses less digits than its factorization.

18306521 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 101322.

The product of its (nonzero) digits is 1440, while the sum is 26.

The square root of 18306521 is about 4278.6120413050. The cubic root of 18306521 is about 263.5533895587.

The spelling of 18306521 in words is "eighteen million, three hundred six thousand, five hundred twenty-one".