21666414 has 64 divisors (see below), whose sum is σ = 56401920. Its totient is φ = 5380320.

The previous prime is 21666397. The next prime is 21666443. The reversal of 21666414 is 41466612.

It is a Curzon number.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 9607 + ... + 11645.

It is an arithmetic number, because the mean of its divisors is an integer number (881280).

Almost surely, 2^21666414 is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21666414, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (28200960).

21666414 is an abundant number, since it is smaller than the sum of its proper divisors (34735506).

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

21666414 is a wasteful number, since it uses less digits than its factorization.

21666414 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2085.

The product of its digits is 6912, while the sum is 30.

The square root of 21666414 is about 4654.7195404235. The cubic root of 21666414 is about 278.7804699008.

It can be divided in two parts, 21 and 666414, that added together give a triangular number (666435 = T₁₁₅₄).

The spelling of 21666414 in words is "twenty-one million, six hundred sixty-six thousand, four hundred fourteen".