1217921251 has 2 divisors, whose sum is σ = 1217921252. Its totient is φ = 1217921250.

The previous prime is 1217921249. The next prime is 1217921311. The reversal of 1217921251 is 1521297121.

It is a weak prime.

It is an emirp because it is prime and its reverse (1521297121) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 1217921251 - 2¹ = 1217921249 is a prime.

Together with 1217921249, it forms a pair of twin primes.

It is not a weakly prime, because it can be changed into another prime (1217921351) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 608960625 + 608960626.

It is an arithmetic number, because the mean of its divisors is an integer number (608960626).

Almost surely, 2^1217921251 is an apocalyptic number.

1217921251 is a deficient number, since it is larger than the sum of its proper divisors (1).

1217921251 is an equidigital number, since it uses as much as digits as its factorization.

1217921251 is an evil number, because the sum of its binary digits is even.

The product of its digits is 2520, while the sum is 31.

The square root of 1217921251 is about 34898.7285011933. The cubic root of 1217921251 is about 1067.9224984908.

The spelling of 1217921251 in words is "one billion, two hundred seventeen million, nine hundred twenty-one thousand, two hundred fifty-one".