21535631 has 4 divisors (see below), whose sum is σ = 23192232. Its totient is φ = 19879032.

The previous prime is 21535621. The next prime is 21535639. The reversal of 21535631 is 13653512.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 21535631 - 2¹⁸ = 21273487 is a prime.

It is a super-2 number, since 2×21535631² = 927566805136322, which contains 22 as substring.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21535631.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21535639) 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 3 ways as a sum of consecutive naturals, for example, 828281 + ... + 828306.

It is an arithmetic number, because the mean of its divisors is an integer number (5798058).

Almost surely, 2^21535631 is an apocalyptic number.

21535631 is a deficient number, since it is larger than the sum of its proper divisors (1656601).

21535631 is a wasteful number, since it uses less digits than its factorization.

21535631 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1656600.

The product of its digits is 2700, while the sum is 26.

The square root of 21535631 is about 4640.6498467348. The cubic root of 21535631 is about 278.2184117657.

The spelling of 21535631 in words is "twenty-one million, five hundred thirty-five thousand, six hundred thirty-one".