21354021 has 24 divisors (see below), whose sum is σ = 33404280. Its totient is φ = 13067136.

The previous prime is 21354019. The next prime is 21354049. The reversal of 21354021 is 12045312.

It can be written as a sum of positive squares in 4 ways, for example, as 4040100 + 17313921 = 2010^2 + 4161^2 .

It is not a de Polignac number, because 21354021 - 2¹ = 21354019 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 21353985 and 21354003.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21354061) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 26395 + ... + 27191.

It is an arithmetic number, because the mean of its divisors is an integer number (1391845).

Almost surely, 2^21354021 is an apocalyptic number.

It is an amenable number.

21354021 is a deficient number, since it is larger than the sum of its proper divisors (12050259).

21354021 is a wasteful number, since it uses less digits than its factorization.

21354021 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1045 (or 1042 counting only the distinct ones).

The product of its (nonzero) digits is 240, while the sum is 18.

The square root of 21354021 is about 4621.0411164585. The cubic root of 21354021 is about 277.4341309452.

Adding to 21354021 its reverse (12045312), we get a palindrome (33399333).

The spelling of 21354021 in words is "twenty-one million, three hundred fifty-four thousand, twenty-one".