21201021 has 24 divisors (see below), whose sum is σ = 32512480. Its totient is φ = 13798512.

The previous prime is 21200987. The next prime is 21201031. The reversal of 21201021 is 12010212.

It is not a de Polignac number, because 21201021 - 2¹⁴ = 21184637 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (9).

It is a Duffinian number.

It is a Curzon number.

It is a junction number, because it is equal to n+sod(n) for n = 21200994 and 21201012.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21201031) 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 23 ways as a sum of consecutive naturals, for example, 9435 + ... + 11463.

Almost surely, 2^21201021 is an apocalyptic number.

It is an amenable number.

21201021 is a deficient number, since it is larger than the sum of its proper divisors (11311459).

21201021 is an equidigital number, since it uses as much as digits as its factorization.

21201021 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2087 (or 2075 counting only the distinct ones).

The product of its (nonzero) digits is 8, while the sum is 9.

The square root of 21201021 is about 4604.4566454686. The cubic root of 21201021 is about 276.7699437012.

Adding to 21201021 its reverse (12010212), we get a palindrome (33211233).

It can be divided in two parts, 2 and 1201021, that multiplied together give a palindrome (2402042).

The spelling of 21201021 in words is "twenty-one million, two hundred one thousand, twenty-one".