21505104 has 30 divisors (see below), whose sum is σ = 60184826. Its totient is φ = 7168320.

The previous prime is 21505063. The next prime is 21505109. The reversal of 21505104 is 40150512.

21505104 is a `hidden beast` number, since 2 + 150 + 510 + 4 = 666.

It can be written as a sum of positive squares in only one way, i.e., 18045504 + 3459600 = 4248^2 + 1860^2 .

It is a Harshad number since it is a multiple of its sum of digits (18).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21505109) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 74527 + ... + 74814.

Almost surely, 2^21505104 is an apocalyptic number.

21505104 is a gapful number since it is divisible by the number (24) formed by its first and last digit.

It is an amenable number.

21505104 is an abundant number, since it is smaller than the sum of its proper divisors (38679722).

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

21505104 is a wasteful number, since it uses less digits than its factorization.

21505104 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 149355 (or 149346 counting only the distinct ones).

The product of its (nonzero) digits is 200, while the sum is 18.

The square root of 21505104 is about 4637.3595935618. The cubic root of 21505104 is about 278.0868903555.

Adding to 21505104 its reverse (40150512), we get a palindrome (61655616).

It can be divided in two parts, 21505 and 104, that added together give a square (21609 = 147²).

The spelling of 21505104 in words is "twenty-one million, five hundred five thousand, one hundred four".