18871921 has 8 divisors (see below), whose sum is σ = 21034080. Its totient is φ = 16826688.

The previous prime is 18871913. The next prime is 18871927. The reversal of 18871921 is 12917881.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 18871921 - 2³ = 18871913 is a prime.

It is a super-2 number, since 2×18871921² = 712298804460482, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (18871927) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 28891 + ... + 29536.

It is an arithmetic number, because the mean of its divisors is an integer number (2629260).

Almost surely, 2^18871921 is an apocalyptic number.

It is an amenable number.

18871921 is a deficient number, since it is larger than the sum of its proper divisors (2162159).

18871921 is a wasteful number, since it uses less digits than its factorization.

18871921 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 58463.

The product of its digits is 8064, while the sum is 37.

The square root of 18871921 is about 4344.1824317126. The cubic root of 18871921 is about 266.2392226750.

The spelling of 18871921 in words is "eighteen million, eight hundred seventy-one thousand, nine hundred twenty-one".