21354251 has 2 divisors, whose sum is σ = 21354252. Its totient is φ = 21354250.

The previous prime is 21354247. The next prime is 21354293. The reversal of 21354251 is 15245312.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21354251 - 2² = 21354247 is a prime.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (21354241) 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, 10677125 + 10677126.

It is an arithmetic number, because the mean of its divisors is an integer number (10677126).

Almost surely, 2^21354251 is an apocalyptic number.

21354251 is a deficient number, since it is larger than the sum of its proper divisors (1).

21354251 is an equidigital number, since it uses as much as digits as its factorization.

21354251 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 1200, while the sum is 23.

The square root of 21354251 is about 4621.0660025583. The cubic root of 21354251 is about 277.4351270046.

Adding to 21354251 its reverse (15245312), we get a palindrome (36599563).

The spelling of 21354251 in words is "twenty-one million, three hundred fifty-four thousand, two hundred fifty-one".