21040635 has 32 divisors (see below), whose sum is σ = 41974272. Its totient is φ = 8743680.

The previous prime is 21040633. The next prime is 21040651. The reversal of 21040635 is 53604012.

It is a happy number.

It is not a de Polignac number, because 21040635 - 2¹ = 21040633 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (21).

It is not an unprimeable number, because it can be changed into a prime (21040633) 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 31 ways as a sum of consecutive naturals, for example, 7954 + ... + 10263.

It is an arithmetic number, because the mean of its divisors is an integer number (1311696).

Almost surely, 2^21040635 is an apocalyptic number.

21040635 is a deficient number, since it is larger than the sum of its proper divisors (20933637).

21040635 is a wasteful number, since it uses less digits than its factorization.

21040635 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 18243.

The product of its (nonzero) digits is 720, while the sum is 21.

The square root of 21040635 is about 4587.0071942390. The cubic root of 21040635 is about 276.0702535926.

Adding to 21040635 its reverse (53604012), we get a palindrome (74644647).

The spelling of 21040635 in words is "twenty-one million, forty thousand, six hundred thirty-five".