18261391 has 4 divisors (see below), whose sum is σ = 18273592. Its totient is φ = 18249192.

The previous prime is 18261389. The next prime is 18261407. The reversal of 18261391 is 19316281.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 19316281 = 1117 ⋅17293.

It is a cyclic number.

It is not a de Polignac number, because 18261391 - 2¹ = 18261389 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 (18261301) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 3480 + ... + 6973.

It is an arithmetic number, because the mean of its divisors is an integer number (4568398).

Almost surely, 2^18261391 is an apocalyptic number.

18261391 is a deficient number, since it is larger than the sum of its proper divisors (12201).

18261391 is a wasteful number, since it uses less digits than its factorization.

18261391 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 12200.

The product of its digits is 2592, while the sum is 31.

The square root of 18261391 is about 4273.3348803949. The cubic root of 18261391 is about 263.3366370715.

The spelling of 18261391 in words is "eighteen million, two hundred sixty-one thousand, three hundred ninety-one".