21609124 has 12 divisors (see below), whose sum is σ = 37862748. Its totient is φ = 10791200.

The previous prime is 21609109. The next prime is 21609131. The reversal of 21609124 is 42190612.

It can be written as a sum of positive squares in 2 ways, for example, as 12110400 + 9498724 = 3480^2 + 3082^2 .

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 894 + ... + 6634.

It is an arithmetic number, because the mean of its divisors is an integer number (3155229).

Almost surely, 2^21609124 is an apocalyptic number.

It is an amenable number.

21609124 is a deficient number, since it is larger than the sum of its proper divisors (16253624).

21609124 is a wasteful number, since it uses less digits than its factorization.

21609124 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 6686 (or 6684 counting only the distinct ones).

The product of its (nonzero) digits is 864, while the sum is 25.

The square root of 21609124 is about 4648.5614979260. The cubic root of 21609124 is about 278.5345373269.

Adding to 21609124 its reverse (42190612), we get a palindrome (63799736).

The spelling of 21609124 in words is "twenty-one million, six hundred nine thousand, one hundred twenty-four".