21133531 has 4 divisors (see below), whose sum is σ = 21221464. Its totient is φ = 21045600.

The previous prime is 21133523. The next prime is 21133559. The reversal of 21133531 is 13533112.

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 21133531 - 2³ = 21133523 is a prime.

It is a super-2 number, since 2×21133531² = 893252265055922, which contains 22 as substring.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21133499 and 21133508.

It is not an unprimeable number, because it can be changed into a prime (21133561) 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, 43605 + ... + 44086.

It is an arithmetic number, because the mean of its divisors is an integer number (5305366).

Almost surely, 2^21133531 is an apocalyptic number.

21133531 is a deficient number, since it is larger than the sum of its proper divisors (87933).

21133531 is an equidigital number, since it uses as much as digits as its factorization.

21133531 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 87932.

The product of its digits is 270, while the sum is 19.

The square root of 21133531 is about 4597.1220344907. The cubic root of 21133531 is about 276.4759474928.

Adding to 21133531 its reverse (13533112), we get a palindrome (34666643).

The spelling of 21133531 in words is "twenty-one million, one hundred thirty-three thousand, five hundred thirty-one".