18981397 has 4 divisors (see below), whose sum is σ = 18996160. Its totient is φ = 18966636.

The previous prime is 18981377. The next prime is 18981427. The reversal of 18981397 is 79318981.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 18981397 - 2¹¹ = 18979349 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 (18981307) 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, 5247 + ... + 8092.

It is an arithmetic number, because the mean of its divisors is an integer number (4749040).

Almost surely, 2^18981397 is an apocalyptic number.

It is an amenable number.

18981397 is a deficient number, since it is larger than the sum of its proper divisors (14763).

18981397 is a wasteful number, since it uses less digits than its factorization.

18981397 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 14762.

The product of its digits is 108864, while the sum is 46.

The square root of 18981397 is about 4356.7645105055. The cubic root of 18981397 is about 266.7530482306.

The spelling of 18981397 in words is "eighteen million, nine hundred eighty-one thousand, three hundred ninety-seven".