21523385 has 16 divisors (see below), whose sum is σ = 28029456. Its totient is φ = 15771648.

The previous prime is 21523361. The next prime is 21523387. The reversal of 21523385 is 58332512.

It can be written as a sum of positive squares in 8 ways, for example, as 169744 + 21353641 = 412^2 + 4621^2 .

It is a cyclic number.

It is not a de Polignac number, because 21523385 - 2¹⁸ = 21261241 is a prime.

It is a super-2 number, since 2×21523385² = 926512203716450, which contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (21523387) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 7697 + ... + 10113.

It is an arithmetic number, because the mean of its divisors is an integer number (1751841).

Almost surely, 2^21523385 is an apocalyptic number.

It is an amenable number.

21523385 is a deficient number, since it is larger than the sum of its proper divisors (6506071).

21523385 is a wasteful number, since it uses less digits than its factorization.

21523385 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2572.

The product of its digits is 7200, while the sum is 29.

The square root of 21523385 is about 4639.3302318330. The cubic root of 21523385 is about 278.1656664855.

Adding to 21523385 its reverse (58332512), we get a palindrome (79855897).

The spelling of 21523385 in words is "twenty-one million, five hundred twenty-three thousand, three hundred eighty-five".