21101251 has 2 divisors, whose sum is σ = 21101252. Its totient is φ = 21101250.

The previous prime is 21101243. The next prime is 21101257. The reversal of 21101251 is 15210112.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21101251 - 2³ = 21101243 is a prime.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (21101257) 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 as a sum of consecutive naturals, namely, 10550625 + 10550626.

It is an arithmetic number, because the mean of its divisors is an integer number (10550626).

Almost surely, 2^21101251 is an apocalyptic number.

21101251 is a deficient number, since it is larger than the sum of its proper divisors (1).

21101251 is an equidigital number, since it uses as much as digits as its factorization.

21101251 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 20, while the sum is 13.

The square root of 21101251 is about 4593.6098005817. The cubic root of 21101251 is about 276.3351098296.

Adding to 21101251 its reverse (15210112), we get a palindrome (36311363).

The spelling of 21101251 in words is "twenty-one million, one hundred one thousand, two hundred fifty-one".