21969218 has 4 divisors (see below), whose sum is σ = 32953830. Its totient is φ = 10984608.

The previous prime is 21969203. The next prime is 21969221. The reversal of 21969218 is 81296912.

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., 21224449 + 744769 = 4607^2 + 863^2 .

It is a Curzon number.

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 5492303 + ... + 5492306.

Almost surely, 2^21969218 is an apocalyptic number.

21969218 is a deficient number, since it is larger than the sum of its proper divisors (10984612).

21969218 is a wasteful number, since it uses less digits than its factorization.

21969218 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 10984611.

The product of its digits is 15552, while the sum is 38.

The square root of 21969218 is about 4687.1332389852. The cubic root of 21969218 is about 280.0731866511.

The spelling of 21969218 in words is "twenty-one million, nine hundred sixty-nine thousand, two hundred eighteen".