21126493 has 4 divisors (see below), whose sum is σ = 21141148. Its totient is φ = 21111840.

The previous prime is 21126487. The next prime is 21126517. The reversal of 21126493 is 39462112.

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 14760964 + 6365529 = 3842^2 + 2523^2 .

It is a cyclic number.

It is not a de Polignac number, because 21126493 - 2¹⁷ = 20995421 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21126403) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 4896 + ... + 8137.

It is an arithmetic number, because the mean of its divisors is an integer number (5285287).

Almost surely, 2^21126493 is an apocalyptic number.

It is an amenable number.

21126493 is a deficient number, since it is larger than the sum of its proper divisors (14655).

21126493 is a wasteful number, since it uses less digits than its factorization.

21126493 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 14654.

The product of its digits is 2592, while the sum is 28.

The square root of 21126493 is about 4596.3564918313. The cubic root of 21126493 is about 276.4452529256.

The spelling of 21126493 in words is "twenty-one million, one hundred twenty-six thousand, four hundred ninety-three".