21753021 has 8 divisors (see below), whose sum is σ = 29270560. Its totient is φ = 14368752.

The previous prime is 21753007. The next prime is 21753023. The reversal of 21753021 is 12035712.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 21753021 - 2⁷ = 21752893 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 (21753023) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 32935 + ... + 33588.

It is an arithmetic number, because the mean of its divisors is an integer number (3658820).

Almost surely, 2^21753021 is an apocalyptic number.

It is an amenable number.

21753021 is a deficient number, since it is larger than the sum of its proper divisors (7517539).

21753021 is a wasteful number, since it uses less digits than its factorization.

21753021 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 66635.

The product of its (nonzero) digits is 420, while the sum is 21.

The square root of 21753021 is about 4664.0134004953. The cubic root of 21753021 is about 279.1514317767.

Adding to 21753021 its reverse (12035712), we get a palindrome (33788733).

The spelling of 21753021 in words is "twenty-one million, seven hundred fifty-three thousand, twenty-one".