21988784 has 10 divisors (see below), whose sum is σ = 42603300. Its totient is φ = 10994384.

The previous prime is 21988777. The next prime is 21988789. The reversal of 21988784 is 48788912.

It is not an unprimeable number, because it can be changed into a prime (21988789) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 687134 + ... + 687165.

It is an arithmetic number, because the mean of its divisors is an integer number (4260330).

Almost surely, 2^21988784 is an apocalyptic number.

It is an amenable number.

21988784 is a deficient number, since it is larger than the sum of its proper divisors (20614516).

21988784 is a wasteful number, since it uses less digits than its factorization.

21988784 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1374307 (or 1374301 counting only the distinct ones).

The product of its digits is 258048, while the sum is 47.

The square root of 21988784 is about 4689.2199777788. The cubic root of 21988784 is about 280.1563072846.

The spelling of 21988784 in words is "twenty-one million, nine hundred eighty-eight thousand, seven hundred eighty-four".