21135537 has 12 divisors (see below), whose sum is σ = 30612660. Its totient is φ = 14051808.

The previous prime is 21135503. The next prime is 21135553. The reversal of 21135537 is 73553112.

It can be written as a sum of positive squares in 2 ways, for example, as 4562496 + 16573041 = 2136^2 + 4071^2 .

It is not a de Polignac number, because 21135537 - 2¹⁰ = 21134513 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21135537.

It is not an unprimeable number, because it can be changed into a prime (21135337) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 483 + ... + 6519.

It is an arithmetic number, because the mean of its divisors is an integer number (2551055).

Almost surely, 2^21135537 is an apocalyptic number.

It is an amenable number.

21135537 is a deficient number, since it is larger than the sum of its proper divisors (9477123).

21135537 is a wasteful number, since it uses less digits than its factorization.

21135537 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 6432 (or 6429 counting only the distinct ones).

The product of its digits is 3150, while the sum is 27.

The square root of 21135537 is about 4597.3402092949. The cubic root of 21135537 is about 276.4846949379.

Adding to 21135537 its reverse (73553112), we get a palindrome (94688649).

The spelling of 21135537 in words is "twenty-one million, one hundred thirty-five thousand, five hundred thirty-seven".