21938218 has 4 divisors (see below), whose sum is σ = 32907330. Its totient is φ = 10969108.

The previous prime is 21938207. The next prime is 21938243. The reversal of 21938218 is 81283912.

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

It can be written as a sum of positive squares in only one way, i.e., 20820969 + 1117249 = 4563^2 + 1057^2 .

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 5484553 + ... + 5484556.

Almost surely, 2^21938218 is an apocalyptic number.

21938218 is a deficient number, since it is larger than the sum of its proper divisors (10969112).

21938218 is a wasteful number, since it uses less digits than its factorization.

21938218 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 10969111.

The product of its digits is 6912, while the sum is 34.

The square root of 21938218 is about 4683.8251461813. The cubic root of 21938218 is about 279.9413907941.

The spelling of 21938218 in words is "twenty-one million, nine hundred thirty-eight thousand, two hundred eighteen".