21245021 has 8 divisors (see below), whose sum is σ = 25558080. Its totient is φ = 17251488.

The previous prime is 21244999. The next prime is 21245027. The reversal of 21245021 is 12054212.

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

It is a cyclic number.

It is not a de Polignac number, because 21245021 - 2¹⁰ = 21243997 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21245027) 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 7 ways as a sum of consecutive naturals, for example, 79736 + ... + 80001.

It is an arithmetic number, because the mean of its divisors is an integer number (3194760).

Almost surely, 2^21245021 is an apocalyptic number.

It is an amenable number.

21245021 is a deficient number, since it is larger than the sum of its proper divisors (4313059).

21245021 is a wasteful number, since it uses less digits than its factorization.

21245021 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 159763.

The product of its (nonzero) digits is 160, while the sum is 17.

The square root of 21245021 is about 4609.2321486339. The cubic root of 21245021 is about 276.9612782393.

Adding to 21245021 its reverse (12054212), we get a palindrome (33299233).

The spelling of 21245021 in words is "twenty-one million, two hundred forty-five thousand, twenty-one".