21139218 has 20 divisors (see below), whose sum is σ = 47367870. Its totient is φ = 7046352.

The previous prime is 21139213. The next prime is 21139243. The reversal of 21139218 is 81293112.

It can be written as a sum of positive squares in only one way, i.e., 18122049 + 3017169 = 4257^2 + 1737^2 .

It is a Harshad number since it is a multiple of its sum of digits (27).

It is a junction number, because it is equal to n+sod(n) for n = 21139191 and 21139200.

It is not an unprimeable number, because it can be changed into a prime (21139213) by changing a digit.

It is a polite number, since it can be written in 9 ways as a sum of consecutive naturals, for example, 65083 + ... + 65406.

Almost surely, 2^21139218 is an apocalyptic number.

21139218 is an abundant number, since it is smaller than the sum of its proper divisors (26228652).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21139218 is a wasteful number, since it uses less digits than its factorization.

21139218 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 130503 (or 130494 counting only the distinct ones).

The product of its digits is 864, while the sum is 27.

The square root of 21139218 is about 4597.7405320440. The cubic root of 21139218 is about 276.5007450164.

The spelling of 21139218 in words is "twenty-one million, one hundred thirty-nine thousand, two hundred eighteen".