1221320251 has 2 divisors, whose sum is σ = 1221320252. Its totient is φ = 1221320250.

The previous prime is 1221320227. The next prime is 1221320281. The reversal of 1221320251 is 1520231221.

It is a weak prime.

It is an emirp because it is prime and its reverse (1520231221) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 1221320251 - 2⁹ = 1221319739 is a prime.

It is not a weakly prime, because it can be changed into another prime (1221320281) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 610660125 + 610660126.

It is an arithmetic number, because the mean of its divisors is an integer number (610660126).

Almost surely, 2^1221320251 is an apocalyptic number.

1221320251 is a deficient number, since it is larger than the sum of its proper divisors (1).

1221320251 is an equidigital number, since it uses as much as digits as its factorization.

1221320251 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 1221320251 is about 34947.3926209095. The cubic root of 1221320251 is about 1068.9150358502.

Adding to 1221320251 its reverse (1520231221), we get a palindrome (2741551472).

The spelling of 1221320251 in words is "one billion, two hundred twenty-one million, three hundred twenty thousand, two hundred fifty-one".