21311021 has 8 divisors (see below), whose sum is σ = 22191288. Its totient is φ = 20448000.

The previous prime is 21310999. The next prime is 21311033. The reversal of 21311021 is 12011312.

It can be written as a sum of positive squares in 4 ways, for example, as 835396 + 20475625 = 914^2 + 4525^2 .

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 21311021 - 2⁶ = 21310957 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21310993 and 21311011.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21311051) 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, 1760 + ... + 6761.

It is an arithmetic number, because the mean of its divisors is an integer number (2773911).

Almost surely, 2^21311021 is an apocalyptic number.

It is an amenable number.

21311021 is a deficient number, since it is larger than the sum of its proper divisors (880267).

21311021 is an equidigital number, since it uses as much as digits as its factorization.

21311021 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 8623.

The product of its (nonzero) digits is 12, while the sum is 11.

The square root of 21311021 is about 4616.3861406949. The cubic root of 21311021 is about 277.2477853372.

Adding to 21311021 its reverse (12011312), we get a palindrome (33322333).

The spelling of 21311021 in words is "twenty-one million, three hundred eleven thousand, twenty-one".