21250501 has 4 divisors (see below), whose sum is σ = 21461004. Its totient is φ = 21040000.

The previous prime is 21250499. The next prime is 21250511. The reversal of 21250501 is 10505212.

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 16524225 + 4726276 = 4065^2 + 2174^2 .

It is a cyclic number.

It is not a de Polignac number, because 21250501 - 2¹ = 21250499 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 polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 105100 + ... + 105301.

It is an arithmetic number, because the mean of its divisors is an integer number (5365251).

Almost surely, 2^21250501 is an apocalyptic number.

It is an amenable number.

21250501 is a deficient number, since it is larger than the sum of its proper divisors (210503).

21250501 is a wasteful number, since it uses less digits than its factorization.

21250501 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 210502.

The product of its (nonzero) digits is 100, while the sum is 16.

The square root of 21250501 is about 4609.8265694058. The cubic root of 21250501 is about 276.9850895804.

Adding to 21250501 its reverse (10505212), we get a palindrome (31755713).

The spelling of 21250501 in words is "twenty-one million, two hundred fifty thousand, five hundred one".