21220220251 has 2 divisors, whose sum is σ = 21220220252. Its totient is φ = 21220220250.

The previous prime is 21220220239. The next prime is 21220220269. The reversal of 21220220251 is 15202202212.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21220220251 - 2¹⁹ = 21219695963 is a prime.

It is not a weakly prime, because it can be changed into another prime (21260220251) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10610110125 + 10610110126.

It is an arithmetic number, because the mean of its divisors is an integer number (10610110126).

Almost surely, 2^21220220251 is an apocalyptic number.

21220220251 is a deficient number, since it is larger than the sum of its proper divisors (1).

21220220251 is an equidigital number, since it uses as much as digits as its factorization.

21220220251 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 320, while the sum is 19.

Adding to 21220220251 its reverse (15202202212), we get a palindrome (36422422463).

The spelling of 21220220251 in words is "twenty-one billion, two hundred twenty million, two hundred twenty thousand, two hundred fifty-one".