21034021 has 4 divisors (see below), whose sum is σ = 21187692. Its totient is φ = 20880352.

The previous prime is 21034003. The next prime is 21034033. The reversal of 21034021 is 12043012.

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 9541921 + 11492100 = 3089^2 + 3390^2 .

It is a cyclic number.

It is not a de Polignac number, because 21034021 - 2⁵ = 21033989 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21033992 and 21034010.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21034061) 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, 76630 + ... + 76903.

It is an arithmetic number, because the mean of its divisors is an integer number (5296923).

Almost surely, 2^21034021 is an apocalyptic number.

It is an amenable number.

21034021 is a deficient number, since it is larger than the sum of its proper divisors (153671).

21034021 is a wasteful number, since it uses less digits than its factorization.

21034021 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 153670.

The product of its (nonzero) digits is 48, while the sum is 13.

The square root of 21034021 is about 4586.2861881919. The cubic root of 21034021 is about 276.0413235403.

Adding to 21034021 its reverse (12043012), we get a palindrome (33077033).

The spelling of 21034021 in words is "twenty-one million, thirty-four thousand, twenty-one".