21523004 has 6 divisors (see below), whose sum is σ = 37665264. Its totient is φ = 10761500.

The previous prime is 21523001. The next prime is 21523049. The reversal of 21523004 is 40032512.

It is a zygodrome in base 3.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21523001) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 2690372 + ... + 2690379.

It is an arithmetic number, because the mean of its divisors is an integer number (6277544).

Almost surely, 2^21523004 is an apocalyptic number.

It is an amenable number.

21523004 is a deficient number, since it is larger than the sum of its proper divisors (16142260).

21523004 is a wasteful number, since it uses less digits than its factorization.

21523004 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5380755 (or 5380753 counting only the distinct ones).

The product of its (nonzero) digits is 240, while the sum is 17.

The square root of 21523004 is about 4639.2891696897. The cubic root of 21523004 is about 278.1640251430.

Adding to 21523004 its reverse (40032512), we get a palindrome (61555516).

The spelling of 21523004 in words is "twenty-one million, five hundred twenty-three thousand, four".