21026251 has 2 divisors, whose sum is σ = 21026252. Its totient is φ = 21026250.

The previous prime is 21026237. The next prime is 21026267. The reversal of 21026251 is 15262012.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21026251 - 2¹⁷ = 20895179 is a prime.

It is a super-2 number, since 2×21026251² = 884206462230002, which contains 22 as substring.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (21026231) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10513125 + 10513126.

It is an arithmetic number, because the mean of its divisors is an integer number (10513126).

Almost surely, 2^21026251 is an apocalyptic number.

21026251 is a deficient number, since it is larger than the sum of its proper divisors (1).

21026251 is an equidigital number, since it uses as much as digits as its factorization.

21026251 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 240, while the sum is 19.

The square root of 21026251 is about 4585.4390193306. The cubic root of 21026251 is about 276.0073293230.

Adding to 21026251 its reverse (15262012), we get a palindrome (36288263).

It can be divided in two parts, 2 and 1026251, that multiplied together give a palindrome (2052502).

The spelling of 21026251 in words is "twenty-one million, twenty-six thousand, two hundred fifty-one".