21453021 has 12 divisors (see below), whose sum is σ = 31413148. Its totient is φ = 14105664.

The previous prime is 21453017. The next prime is 21453037. The reversal of 21453021 is 12035412.

It can be written as a sum of positive squares in 2 ways, for example, as 10304100 + 11148921 = 3210^2 + 3339^2 .

It is not a de Polignac number, because 21453021 - 2² = 21453017 is a prime.

It is a super-2 number, since 2×21453021² = 920464220052882, 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 = 21452985 and 21453003.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21452021) 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, 15670 + ... + 16983.

Almost surely, 2^21453021 is an apocalyptic number.

It is an amenable number.

21453021 is a deficient number, since it is larger than the sum of its proper divisors (9960127).

21453021 is a wasteful number, since it uses less digits than its factorization.

21453021 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 32732 (or 32729 counting only the distinct ones).

The product of its (nonzero) digits is 240, while the sum is 18.

The square root of 21453021 is about 4631.7406015450. The cubic root of 21453021 is about 277.8622102388.

Adding to 21453021 its reverse (12035412), we get a palindrome (33488433).

It can be divided in two parts, 214 and 53021, that added together give a palindrome (53235).

The spelling of 21453021 in words is "twenty-one million, four hundred fifty-three thousand, twenty-one".