21921418 has 8 divisors (see below), whose sum is σ = 33221412. Its totient is φ = 10847616.

The previous prime is 21921413. The next prime is 21921437. The reversal of 21921418 is 81412912.

It can be written as a sum of positive squares in 2 ways, for example, as 21874329 + 47089 = 4677^2 + 217^2 .

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 (21921413) 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, 56305 + ... + 56692.

Almost surely, 2^21921418 is an apocalyptic number.

21921418 is a deficient number, since it is larger than the sum of its proper divisors (11299994).

21921418 is a wasteful number, since it uses less digits than its factorization.

It is an anagram of its base 11 representation: 21921418 = (11412982)₁₁.

21921418 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 113096.

The product of its digits is 1152, while the sum is 28.

The square root of 21921418 is about 4682.0313967337. The cubic root of 21921418 is about 279.8699140622.

The spelling of 21921418 in words is "twenty-one million, nine hundred twenty-one thousand, four hundred eighteen".