18905309 has 4 divisors (see below), whose sum is σ = 20017404. Its totient is φ = 17793216.

The previous prime is 18905279. The next prime is 18905317. The reversal of 18905309 is 90350981.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 90350981 = 7 ⋅12907283.

It can be written as a sum of positive squares in 2 ways, for example, as 12888100 + 6017209 = 3590^2 + 2453^2 .

It is a cyclic number.

It is not a de Polignac number, because 18905309 - 2⁸ = 18905053 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (18905329) 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, 556022 + ... + 556055.

It is an arithmetic number, because the mean of its divisors is an integer number (5004351).

Almost surely, 2^18905309 is an apocalyptic number.

It is an amenable number.

18905309 is a deficient number, since it is larger than the sum of its proper divisors (1112095).

18905309 is a wasteful number, since it uses less digits than its factorization.

18905309 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1112094.

The product of its (nonzero) digits is 9720, while the sum is 35.

The square root of 18905309 is about 4348.0235739931. The cubic root of 18905309 is about 266.3961393643.

The spelling of 18905309 in words is "eighteen million, nine hundred five thousand, three hundred nine".