21821418 has 12 divisors (see below), whose sum is σ = 47279778. Its totient is φ = 7273800.

The previous prime is 21821413. The next prime is 21821419. The reversal of 21821418 is 81412812.

It can be written as a sum of positive squares in only one way, i.e., 11108889 + 10712529 = 3333^2 + 3273^2 .

It is a super-3 number, since 3×21821418³ (a number of 23 digits) contains 333 as substring.

It is a junction number, because it is equal to n+sod(n) for n = 21821391 and 21821400.

It is not an unprimeable number, because it can be changed into a prime (21821413) 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, 606133 + ... + 606168.

Almost surely, 2^21821418 is an apocalyptic number.

21821418 is an abundant number, since it is smaller than the sum of its proper divisors (25458360).

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

21821418 is a wasteful number, since it uses less digits than its factorization.

21821418 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1212309 (or 1212306 counting only the distinct ones).

The product of its digits is 1024, while the sum is 27.

The square root of 21821418 is about 4671.3400646924. The cubic root of 21821418 is about 279.4436999045.

It can be divided in two parts, 2182 and 1418, that added together give a square (3600 = 60²).

The spelling of 21821418 in words is "twenty-one million, eight hundred twenty-one thousand, four hundred eighteen".