21532021 has 6 divisors (see below), whose sum is σ = 25047510. Its totient is φ = 18455976.

The previous prime is 21532019. The next prime is 21532031. The reversal of 21532021 is 12023512.

It can be written as a sum of positive squares in only one way, i.e., 21022225 + 509796 = 4585^2 + 714^2 .

It is not a de Polignac number, because 21532021 - 2¹ = 21532019 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21531986 and 21532004.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21532031) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 219666 + ... + 219763.

It is an arithmetic number, because the mean of its divisors is an integer number (4174585).

Almost surely, 2^21532021 is an apocalyptic number.

It is an amenable number.

21532021 is a deficient number, since it is larger than the sum of its proper divisors (3515489).

21532021 is an equidigital number, since it uses as much as digits as its factorization.

21532021 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 439443 (or 439436 counting only the distinct ones).

The product of its (nonzero) digits is 120, while the sum is 16.

The square root of 21532021 is about 4640.2608762870. The cubic root of 21532021 is about 278.2028650563.

Adding to 21532021 its reverse (12023512), we get a palindrome (33555533).

The spelling of 21532021 in words is "twenty-one million, five hundred thirty-two thousand, twenty-one".