21221120251 has 2 divisors, whose sum is σ = 21221120252. Its totient is φ = 21221120250.

The previous prime is 21221120203. The next prime is 21221120321. The reversal of 21221120251 is 15202112212.

It is a happy number.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21221120251 - 2²³ = 21212731643 is a prime.

It is not a weakly prime, because it can be changed into another prime (21221120051) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10610560125 + 10610560126.

It is an arithmetic number, because the mean of its divisors is an integer number (10610560126).

Almost surely, 2^21221120251 is an apocalyptic number.

21221120251 is a deficient number, since it is larger than the sum of its proper divisors (1).

21221120251 is an equidigital number, since it uses as much as digits as its factorization.

21221120251 is an evil number, because the sum of its binary digits is even.

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

Adding to 21221120251 its reverse (15202112212), we get a palindrome (36423232463).

The spelling of 21221120251 in words is "twenty-one billion, two hundred twenty-one million, one hundred twenty thousand, two hundred fifty-one".