21664230 has 64 divisors (see below), whose sum is σ = 60300288. Its totient is φ = 4878720.

The previous prime is 21664207. The next prime is 21664267. The reversal of 21664230 is 3246612.

It is a super-2 number, since 2×21664230² = 938677722985800, which contains 22 as substring.

It is a self number, because there is not a number n which added to its sum of digits gives 21664230.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 14184 + ... + 15636.

It is an arithmetic number, because the mean of its divisors is an integer number (942192).

Almost surely, 2^21664230 is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21664230, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (30150144).

21664230 is an abundant number, since it is smaller than the sum of its proper divisors (38636058).

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

21664230 is a wasteful number, since it uses less digits than its factorization.

21664230 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1541.

The product of its (nonzero) digits is 1728, while the sum is 24.

The square root of 21664230 is about 4654.4849339105. The cubic root of 21664230 is about 278.7711024530.

It can be divided in two parts, 216 and 64230, that added together give a palindrome (64446).

The spelling of 21664230 in words is "twenty-one million, six hundred sixty-four thousand, two hundred thirty".