21988828 has 24 divisors (see below), whose sum is σ = 40844160. Its totient is φ = 10335600.

The previous prime is 21988823. The next prime is 21988829. The reversal of 21988828 is 82888912.

It is a Harshad number since it is a multiple of its sum of digits (46).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21988823) 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, 3403 + ... + 7453.

It is an arithmetic number, because the mean of its divisors is an integer number (1701840).

Almost surely, 2^21988828 is an apocalyptic number.

It is an amenable number.

21988828 is a deficient number, since it is larger than the sum of its proper divisors (18855332).

21988828 is a wasteful number, since it uses less digits than its factorization.

21988828 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4137 (or 4135 counting only the distinct ones).

The product of its digits is 147456, while the sum is 46.

The square root of 21988828 is about 4689.2246693883. The cubic root of 21988828 is about 280.1564941506.

It can be divided in two parts, 2198 and 8828, that added together give a triangular number (11026 = T₁₄₈).

The spelling of 21988828 in words is "twenty-one million, nine hundred eighty-eight thousand, eight hundred twenty-eight".