21250541 has 4 divisors (see below), whose sum is σ = 22885212. Its totient is φ = 19615872.

The previous prime is 21250517. The next prime is 21250553. The reversal of 21250541 is 14505212.

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 10824100 + 10426441 = 3290^2 + 3229^2 .

It is a cyclic number.

It is not a de Polignac number, because 21250541 - 2⁶ = 21250477 is a prime.

It is an alternating number because its digits alternate between even and odd.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21250511) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 817316 + ... + 817341.

It is an arithmetic number, because the mean of its divisors is an integer number (5721303).

Almost surely, 2^21250541 is an apocalyptic number.

It is an amenable number.

21250541 is a deficient number, since it is larger than the sum of its proper divisors (1634671).

21250541 is a wasteful number, since it uses less digits than its factorization.

21250541 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1634670.

The product of its (nonzero) digits is 400, while the sum is 20.

The square root of 21250541 is about 4609.8309079618. The cubic root of 21250541 is about 276.9852633708.

Adding to 21250541 its reverse (14505212), we get a palindrome (35755753).

The spelling of 21250541 in words is "twenty-one million, two hundred fifty thousand, five hundred forty-one".