18961309 has 4 divisors (see below), whose sum is σ = 18975100. Its totient is φ = 18947520.

The previous prime is 18961289. The next prime is 18961321. The reversal of 18961309 is 90316981.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 90316981 = 31 ⋅2913451.

It can be written as a sum of positive squares in 2 ways, for example, as 5616900 + 13344409 = 2370^2 + 3653^2 .

It is a cyclic number.

It is not a de Polignac number, because 18961309 - 2¹³ = 18953117 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 (18961339) 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, 4572 + ... + 7669.

It is an arithmetic number, because the mean of its divisors is an integer number (4743775).

Almost surely, 2^18961309 is an apocalyptic number.

It is an amenable number.

18961309 is a deficient number, since it is larger than the sum of its proper divisors (13791).

18961309 is a wasteful number, since it uses less digits than its factorization.

18961309 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 13790.

The product of its (nonzero) digits is 11664, while the sum is 37.

The square root of 18961309 is about 4354.4585197244. The cubic root of 18961309 is about 266.6589134899.

The spelling of 18961309 in words is "eighteen million, nine hundred sixty-one thousand, three hundred nine".