21535537 has 4 divisors (see below), whose sum is σ = 22060836. Its totient is φ = 21010240.

The previous prime is 21535529. The next prime is 21535589. The reversal of 21535537 is 73553512.

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

It can be written as a sum of positive squares in 2 ways, for example, as 7667361 + 13868176 = 2769^2 + 3724^2 .

It is a cyclic number.

It is not a de Polignac number, because 21535537 - 2³ = 21535529 is a prime.

It is a Smith number, since the sum of its digits (31) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21535499 and 21535508.

It is not an unprimeable number, because it can be changed into a prime (21535237) 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 in 3 ways as a sum of consecutive naturals, for example, 262588 + ... + 262669.

It is an arithmetic number, because the mean of its divisors is an integer number (5515209).

Almost surely, 2^21535537 is an apocalyptic number.

It is an amenable number.

21535537 is a deficient number, since it is larger than the sum of its proper divisors (525299).

21535537 is an equidigital number, since it uses as much as digits as its factorization.

21535537 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 525298.

The product of its digits is 15750, while the sum is 31.

The square root of 21535537 is about 4640.6397188319. The cubic root of 21535537 is about 278.2180069703.

The spelling of 21535537 in words is "twenty-one million, five hundred thirty-five thousand, five hundred thirty-seven".