21200251 has 4 divisors (see below), whose sum is σ = 21210552. Its totient is φ = 21189952.

The previous prime is 21200233. The next prime is 21200279. The reversal of 21200251 is 15200212.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21200251 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21200281) 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, 886 + ... + 6571.

It is an arithmetic number, because the mean of its divisors is an integer number (5302638).

Almost surely, 2^21200251 is an apocalyptic number.

21200251 is a deficient number, since it is larger than the sum of its proper divisors (10301).

21200251 is an equidigital number, since it uses as much as digits as its factorization.

21200251 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 10300.

The product of its (nonzero) digits is 40, while the sum is 13.

The square root of 21200251 is about 4604.3730300661. The cubic root of 21200251 is about 276.7665929909.

Adding to 21200251 its reverse (15200212), we get a palindrome (36400463).

The spelling of 21200251 in words is "twenty-one million, two hundred thousand, two hundred fifty-one".