18973981 has 4 divisors (see below), whose sum is σ = 20433532. Its totient is φ = 17514432.

The previous prime is 18973979. The next prime is 18974009. The reversal of 18973981 is 18937981.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 7650756 + 11323225 = 2766^2 + 3365^2 .

It is not a de Polignac number, because 18973981 - 2¹ = 18973979 is a prime.

It is a super-2 number, since 2×18973981² = 720023909976722, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (18973901) 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, 729756 + ... + 729781.

It is an arithmetic number, because the mean of its divisors is an integer number (5108383).

Almost surely, 2^18973981 is an apocalyptic number.

It is an amenable number.

18973981 is a deficient number, since it is larger than the sum of its proper divisors (1459551).

18973981 is a wasteful number, since it uses less digits than its factorization.

18973981 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1459550.

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

The square root of 18973981 is about 4355.9133370626. The cubic root of 18973981 is about 266.7183037157.

The spelling of 18973981 in words is "eighteen million, nine hundred seventy-three thousand, nine hundred eighty-one".