21237218 has 8 divisors (see below), whose sum is σ = 31875420. Its totient is φ = 10612080.

The previous prime is 21237217. The next prime is 21237239. The reversal of 21237218 is 81273212.

It can be written as a sum of positive squares in 2 ways, for example, as 21224449 + 12769 = 4607^2 + 113^2 .

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

It is not an unprimeable number, because it can be changed into a prime (21237217) 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, 4388 + ... + 7856.

Almost surely, 2^21237218 is an apocalyptic number.

21237218 is a deficient number, since it is larger than the sum of its proper divisors (10638202).

21237218 is a wasteful number, since it uses less digits than its factorization.

21237218 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 6532.

The product of its digits is 1344, while the sum is 26.

The square root of 21237218 is about 4608.3856175455. The cubic root of 21237218 is about 276.9273660819.

The spelling of 21237218 in words is "twenty-one million, two hundred thirty-seven thousand, two hundred eighteen".