21640216 has 32 divisors (see below), whose sum is σ = 43923600. Its totient is φ = 9936000.

The previous prime is 21640189. The next prime is 21640219. The reversal of 21640216 is 61204612.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21640219) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 25690 + ... + 26518.

Almost surely, 2^21640216 is an apocalyptic number.

21640216 is a gapful number since it is divisible by the number (26) formed by its first and last digit.

It is an amenable number.

21640216 is an abundant number, since it is smaller than the sum of its proper divisors (22283384).

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

21640216 is a wasteful number, since it uses less digits than its factorization.

21640216 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1099 (or 1095 counting only the distinct ones).

The product of its (nonzero) digits is 576, while the sum is 22.

The square root of 21640216 is about 4651.9045562006. The cubic root of 21640216 is about 278.6680618760.

Adding to 21640216 its reverse (61204612), we get a palindrome (82844828).

The spelling of 21640216 in words is "twenty-one million, six hundred forty thousand, two hundred sixteen".