21529993 has 4 divisors (see below), whose sum is σ = 21540420. Its totient is φ = 21519568.

The previous prime is 21529979. The next prime is 21529997. The reversal of 21529993 is 39992512.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length.

It can be written as a sum of positive squares in 2 ways, for example, as 480249 + 21049744 = 693^2 + 4588^2 .

It is a cyclic number.

It is not a de Polignac number, because 21529993 - 2⁹ = 21529481 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21529997) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 958 + ... + 6631.

It is an arithmetic number, because the mean of its divisors is an integer number (5385105).

Almost surely, 2^21529993 is an apocalyptic number.

It is an amenable number.

21529993 is a deficient number, since it is larger than the sum of its proper divisors (10427).

21529993 is an equidigital number, since it uses as much as digits as its factorization.

21529993 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 10426.

The product of its digits is 43740, while the sum is 40.

The square root of 21529993 is about 4640.0423489447. The cubic root of 21529993 is about 278.1941305746.

It can be divided in two parts, 21529 and 993, that added together give a palindrome (22522).

The spelling of 21529993 in words is "twenty-one million, five hundred twenty-nine thousand, nine hundred ninety-three".