21453913 has 4 divisors (see below), whose sum is σ = 23104228. Its totient is φ = 19803600.

The previous prime is 21453911. The next prime is 21453919. The reversal of 21453913 is 31935412.

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 12194064 + 9259849 = 3492^2 + 3043^2 .

It is a cyclic number.

It is not a de Polignac number, because 21453913 - 2¹ = 21453911 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21453911) 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, 825138 + ... + 825163.

It is an arithmetic number, because the mean of its divisors is an integer number (5776057).

Almost surely, 2^21453913 is an apocalyptic number.

It is an amenable number.

21453913 is a deficient number, since it is larger than the sum of its proper divisors (1650315).

21453913 is a wasteful number, since it uses less digits than its factorization.

21453913 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1650314.

The product of its digits is 3240, while the sum is 28.

The square root of 21453913 is about 4631.8368926377. The cubic root of 21453913 is about 277.8660612839.

It can be divided in two parts, 21453 and 913, that added together give a triangular number (22366 = T₂₁₁).

The spelling of 21453913 in words is "twenty-one million, four hundred fifty-three thousand, nine hundred thirteen".