21221012251 has 2 divisors, whose sum is σ = 21221012252. Its totient is φ = 21221012250.

The previous prime is 21221012213. The next prime is 21221012269. The reversal of 21221012251 is 15221012212.

It is a happy number.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21221012251 - 2¹⁷ = 21220881179 is a prime.

It is not a weakly prime, because it can be changed into another prime (21221012551) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10610506125 + 10610506126.

It is an arithmetic number, because the mean of its divisors is an integer number (10610506126).

Almost surely, 2^21221012251 is an apocalyptic number.

21221012251 is a deficient number, since it is larger than the sum of its proper divisors (1).

21221012251 is an equidigital number, since it uses as much as digits as its factorization.

21221012251 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 160, while the sum is 19.

Adding to 21221012251 its reverse (15221012212), we get a palindrome (36442024463).

The spelling of 21221012251 in words is "twenty-one billion, two hundred twenty-one million, twelve thousand, two hundred fifty-one".