21109544 has 8 divisors (see below), whose sum is σ = 39580410. Its totient is φ = 10554768.

The previous prime is 21109493. The next prime is 21109549. The reversal of 21109544 is 44590112.

It can be written as a sum of positive squares in only one way, i.e., 20702500 + 407044 = 4550^2 + 638^2 .

It is a tau number, because it is divible by the number of its divisors (8).

It is a super-2 number, since 2×21109544² = 891225695775872, which contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (21109549) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 1319339 + ... + 1319354.

Almost surely, 2^21109544 is an apocalyptic number.

It is an amenable number.

21109544 is a deficient number, since it is larger than the sum of its proper divisors (18470866).

21109544 is a wasteful number, since it uses less digits than its factorization.

21109544 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2638699 (or 2638695 counting only the distinct ones).

The product of its (nonzero) digits is 1440, while the sum is 26.

The square root of 21109544 is about 4594.5123789147. The cubic root of 21109544 is about 276.3713058971.

Adding to 21109544 its reverse (44590112), we get a palindrome (65699656).

The spelling of 21109544 in words is "twenty-one million, one hundred nine thousand, five hundred forty-four".