18997971 has 4 divisors (see below), whose sum is σ = 25330632. Its totient is φ = 12665312.

The previous prime is 18997969. The next prime is 18997973. The reversal of 18997971 is 17979981.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 17979981 = 3 ⋅5993327.

It is an interprime number because it is at equal distance from previous prime (18997969) and next prime (18997973).

It is a cyclic number.

It is not a de Polignac number, because 18997971 - 2¹ = 18997969 is a prime.

It is not an unprimeable number, because it can be changed into a prime (18997973) 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, 3166326 + ... + 3166331.

It is an arithmetic number, because the mean of its divisors is an integer number (6332658).

Almost surely, 2^18997971 is an apocalyptic number.

18997971 is a deficient number, since it is larger than the sum of its proper divisors (6332661).

18997971 is an equidigital number, since it uses as much as digits as its factorization.

18997971 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 6332660.

The product of its digits is 285768, while the sum is 51.

The square root of 18997971 is about 4358.6661950647. Note that the first 3 decimals coincide. The cubic root of 18997971 is about 266.8306659605.

It can be divided in two parts, 1899 and 7971, that added together give a triangular number (9870 = T₁₄₀).

The spelling of 18997971 in words is "eighteen million, nine hundred ninety-seven thousand, nine hundred seventy-one".