21533413 has 4 divisors (see below), whose sum is σ = 23491008. Its totient is φ = 19575820.

The previous prime is 21533363. The next prime is 21533431. The reversal of 21533413 is 31433512.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a de Polignac number, because none of the positive numbers 2^k-21533413 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21533443) 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, 978781 + ... + 978802.

It is an arithmetic number, because the mean of its divisors is an integer number (5872752).

Almost surely, 2^21533413 is an apocalyptic number.

It is an amenable number.

21533413 is a deficient number, since it is larger than the sum of its proper divisors (1957595).

21533413 is a wasteful number, since it uses less digits than its factorization.

21533413 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1957594.

The product of its digits is 1080, while the sum is 22.

The square root of 21533413 is about 4640.4108654299. The cubic root of 21533413 is about 278.2088600043.

Adding to 21533413 its reverse (31433512), we get a palindrome (52966925).

Subtracting 21533413 from its reverse (31433512), we obtain a palindrome (9900099).

The spelling of 21533413 in words is "twenty-one million, five hundred thirty-three thousand, four hundred thirteen".