21988644 has 24 divisors (see below), whose sum is σ = 53538240. Its totient is φ = 7010784.

The previous prime is 21988627. The next prime is 21988649. The reversal of 21988644 is 44688912.

It is a junction number, because it is equal to n+sod(n) for n = 21988596 and 21988605.

It is not an unprimeable number, because it can be changed into a prime (21988649) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 39559 + ... + 40110.

It is an arithmetic number, because the mean of its divisors is an integer number (2230760).

Almost surely, 2^21988644 is an apocalyptic number.

It is an amenable number.

21988644 is an abundant number, since it is smaller than the sum of its proper divisors (31549596).

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

21988644 is a wasteful number, since it uses less digits than its factorization.

21988644 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 79699 (or 79697 counting only the distinct ones).

The product of its digits is 110592, while the sum is 42.

The square root of 21988644 is about 4689.2050498992. The cubic root of 21988644 is about 280.1557127092.

The spelling of 21988644 in words is "twenty-one million, nine hundred eighty-eight thousand, six hundred forty-four".