16918421 has 6 divisors (see below), whose sum is σ = 18320130. Its totient is φ = 15616848.

The previous prime is 16918399. The next prime is 16918423. The reversal of 16918421 is 12481961.

It can be written as a sum of positive squares in 3 ways, for example, as 1030225 + 15888196 = 1015^2 + 3986^2 .

It is not a de Polignac number, because 16918421 - 2⁶ = 16918357 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 (16918423) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 49886 + ... + 50223.

It is an arithmetic number, because the mean of its divisors is an integer number (3053355).

Almost surely, 2^16918421 is an apocalyptic number.

It is an amenable number.

16918421 is a deficient number, since it is larger than the sum of its proper divisors (1401709).

16918421 is a wasteful number, since it uses less digits than its factorization.

16918421 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 100135 (or 100122 counting only the distinct ones).

The product of its digits is 3456, while the sum is 32.

The square root of 16918421 is about 4113.2008217445. The cubic root of 16918421 is about 256.7162002187.

The spelling of 16918421 in words is "sixteen million, nine hundred eighteen thousand, four hundred twenty-one".