21410021 has 4 divisors (see below), whose sum is σ = 22669452. Its totient is φ = 20150592.

The previous prime is 21410009. The next prime is 21410023. The reversal of 21410021 is 12001412.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 19936225 + 1473796 = 4465^2 + 1214^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21410021 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21409984 and 21410011.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21410023) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 629690 + ... + 629723.

It is an arithmetic number, because the mean of its divisors is an integer number (5667363).

Almost surely, 2^21410021 is an apocalyptic number.

It is an amenable number.

21410021 is a deficient number, since it is larger than the sum of its proper divisors (1259431).

21410021 is a wasteful number, since it uses less digits than its factorization.

21410021 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1259430.

The product of its (nonzero) digits is 16, while the sum is 11.

The square root of 21410021 is about 4627.0963897459. The cubic root of 21410021 is about 277.6764389393.

Adding to 21410021 its reverse (12001412), we get a palindrome (33411433).

The spelling of 21410021 in words is "twenty-one million, four hundred ten thousand, twenty-one".